In these pages it is contended that neither brilliant coloration nor any other form of ornamentation is to be ascribed to the direct action of “Sexual Selection.” That is to say, such conspicuous12 features have not been dependent on the action of female choice for their survival and development, but are rather the “expression points” of the internal, inherent growth variations, which, not being inimical to the welfare of the species, have been free to pursue their development in any direction which apparent chance may dictate13.
The Butterflies and Moths15 well illustrate16 this in regard to coloration, for scent17, not colour, would seem to be their principal source of information as to the outer world. The Beetles are no less instructive; for these 209creatures, though they contain numerous highly-coloured and some exquisitely18 beautiful species, are more remarkable for their bizarre shapes, and it seems impossible to regard these as the products of sexual selection. Yet this is the interpretation19 of their origin which, in the judgment20 of Darwin, we must adopt. He evidently had misgivings21 as to the correctness of this view; but it must be remembered that in reviewing the facts relating to these lower orders of Creation he was biased22 by the evidence which he had brought together in regard to the behaviour of the higher groups under the stimulus23 of sexual emotion. Convinced that female choice obtained here, he was but following the logical result of such conclusions in postulating24 the same factor wherever it could conceivably be applied25. The most formidable critic of the Darwinian theory of Sexual Selection was Darwin himself. The dominant26 ambition in all his work was to explain his facts, not to establish his theory; and he was convinced that his theory of Sexual Selection did achieve that end; though there were cases where the evidence he was analysing seemed less clear than in others. That the Beetles presented difficulties is evident from his comments thereon. He was puzzled by the vivid coloration which some species present. “They may serve,” he remarks, “as a warning or means of recognition ... as with Beetles the colours of the two sexes are generally alike, we have no evidence that they have been gained through sexual selection; but this is at least possible, for they may have been developed in one sex and then transferred to the other; and this view is even in some degree probable in those groups which possess other well-marked secondary sexual characters....
“Some Longicorns, especially certain Prionid?, offer 210an exception to the rule that the sexes of Beetles do not differ in colour. Most of these insects are large and splendidly coloured. The males of the genus Pyrodes ... are generally redder but rather duller than the females, the latter being coloured of a more or less splendid golden-green. On the other hand, in one species the male is golden-green, the female being tinted28 with red and purple. In the genus Esmeralda the sexes differ so greatly in colour that they have been ranked as distinct species: in one species both are of a beautiful shining green, but the male has a red thorax. On the whole, as far as I could judge, the females of those Prionid? in which the sexes differ are coloured more richly than the males, and this does not accord with the common rule in regard to colour when acquired through sexual selection.”
While there is nothing very remarkable in the two sexes being coloured alike, it is certainly strange to find the female more brilliantly coloured than the male. And this because among the higher vertebrates, as among the birds, the female exceeds in brilliance29 only where she also plays the r?le of wooer instead of wooed; leaving to the male the whole responsibility of rearing the family. With the Beetles the family has to rear itself, parental30 care being limited to the right disposal of the eggs. By some change in the character of the germ-plasm the females may have, in these cases, acquired more “maleness,” more of the qualities which are answerable for the secondary sexual characters of the male, or, what seems rather to be the case here, a result like that which has been reached in certain of the Pigeons and Parrots has been arrived at. That is to say, the tendency to intensification31 of pigment32 in the female struck out a new line, instead of following 211that of the male. This rather rare form of sexual dimorphism is also met with, it will be remembered, among the Butterflies and Moths.
While brilliant colour is the more usual form of ornament among the Beetles, there are many species wherein the males have developed enormous horns, or have greatly exaggerated the length of the jaws; and these outgrowths give the impression of a formidable armature, but so far as the evidence goes this is by no means the case. They must therefore be relegated33 to the category of “ornaments34,” though the term “excrescences” would more fittingly apply to them, for they are “ornaments” only from a human standpoint. At any rate, there is no evidence whatever that they serve to enhance their possessors in the eyes of the females.
In relation to the Sexual Selection theory these excrescences are of quite exceptional interest, for they throw a strong light on the meaning of ornament, such as obtains among birds, which seem to show a consciousness of its existence and effectiveness. Darwin argued from the birds to the Beetles. Convinced that the gorgeous crests35 and trains and vivid colours were appreciated by the females of the former, he was impelled36 to believe that the ornaments of the latter had developed in like case by the fostering influences of the females. Similarly, from the evidence as to the use of horns in the case of mammals, and spurs in the case of birds, he was induced to believe that the horn-like outgrowths of Beetles had been attained38 by like influences. But in both kinds of cases, he could only infer their action, for he could discover no really decisive instances of conquest either by display or by battle, such as he was able to produce in the case of the higher animals. Had chance directed his attention in the beginning either to the Warblers 212among the birds, or the beetles among the insects, his interpretation of the action of sexual selection, it is more than probable, would have been materially different from that developed in the “Descent of Man.” No additions of any importance have been added to the facts he so laboriously39 collected.
As touching40 the “horns” it should be remarked that these may arise either from the head or from the thorax, or from both, and sometimes even from the under surface of the body.
One of the most remarkable instances of these singular outgrowths is that of the Hercules Beetle3 (Dynastes hercules) of the West Indies and tropical America. Herein the roof of the head is prolonged into a great upturned beam bearing tooth-like prominences41, and the top of this is opposed to a still more massive beam, whose base covers the whole roof of the thorax, and whose tip extends far beyond that projecting from the head. A pair of “teeth” point downwards42 from the middle of this beam, whose under surface is thickly covered with short chestnut43-coloured hairs forming a brush-like surface. In another, Copris isidis, the head bears two short, rhinoceros-like horns, and the thorax a short, triangular44 overhanging ledge45: in Phan?us jaunus there is a single horn on the head, and the thorax bears two short, forwardly-projecting blades, one on each side; while in Onthophagus rangifer—the Reindeer46 Beetle—the head bears a pair of horns curiously47 like the antlers of a deer. One might cite many such instances, all varying in detail, but these will suffice.
Darwin, in commenting on these structures, remarked: “The extraordinary size of the horns and their widely 213different structure in closely-allied48 forms indicate that they have been formed for some purpose; but their excessive variability in the males of the same species leads to the inference that this purpose cannot be of a definite nature. The horns do not show marks of friction49, as if used for any ordinary work. Some authors suppose that as the males wander about much more than the females, they require horns as a defence against their enemies; but as the horns are often blunt, they do not seem well adapted for defence. The most obvious conjecture50 is that they are used by the males for fighting together, but the males have never been observed to fight, nor could Mr. Bates, after a careful examination of numerous species, find any sufficient evidence, in their mutilated or broken condition, of their having been thus used. If the males had been habitual52 fighters, the size of their bodies would probably have been increased through sexual selection, so as to have exceeded that of the females; but Mr. Bates, after comparing the two sexes in above a hundred species of the Coprid?, did not find any marked difference in this respect amongst well-developed individuals. In Lethrus, moreover, a Beetle belonging to the same great division of the Lamellicorns, the males are known to fight, but are not provided with horns, though their mandibles are much larger than those of the female.
“The conclusion that horns have been acquired as ornaments is that which best agrees with the fact of their having been so immensely, yet not fixedly53, developed—as shown by their extreme variability in the same species This view will at first appear extremely improbable, but we shall ... find with many animals standing54 much higher in the scale, namely, fishes, amphibians55, 214reptiles and birds, that various kinds of crests, knobs, horns and combs have been developed apparently56 for this sole purpose.”
The assumption that these “animals standing much higher in the scale” owe their weapons to the selective action of the females forms the crux57 of the whole Sexual Selection theory in regard to the significance of ornament. The evidence that the intensification of pigment and the eccentricities58 of growth in the shape of crests and frills have a fascinating effect on the female is more than under suspicion; it is discredited59 by the facts which have come to light in regard to behaviour during the periods of sexual exaltation. And there is a growing conviction that this is so. No better proof could be found that “ornaments” can, and do, exist in spite of, rather than because of, the action of “sexual selection.” They are the accidents of this selection, not a part of its machinery60.
Incipient61 horns are found in not a few cases among the females of these insects, while in others, as in the case of the Reindeer Beetle, they are almost as well developed as in the males. This is what one would expect to find if these outgrowths were the result of inherent variations restrained as to their size by natural selection, which eliminates only when this growth penalizes62, by increasing the struggle for existence.
As to the actual behaviour of Beetles when sexually excited but very little information is obtainable; but there are records of species the males of which fight with rivals for the possession of females. Wallace saw two males of Leptorhynchus augustatus, a Beetle with no name in common speech and a long beak63, “fighting for a female, who stood close by busy at her boring. They pushed at each other with their rostra, and clawed 215and thumped64 in the greatest rage.” The smaller male, however, “soon ran away, acknowledging himself vanquished65.” In this case, it is to be noted66, the combatants lacked weapons. With the Stag Beetle it is otherwise, and this species is said to engage in fierce conflicts. Darwin cites an instance where two males were enclosed with one female in a box, when the larger severely67 pinched the smaller one, until he resigned his pretensions68. This being so, it is curious to find that the female, which makes no display of pugnacity69, has the stronger jaws. The fact that there are so few records of fighting among male Beetles, and the absence of injury to the highly-polished surfaces of the horns or jaws where these are conspicuously70 large, seem to indicate that at most no more than a semblance71 of fighting ever takes place. In a North American Stag Beetle (Lucanus elaphus) the jaws, which are greatly developed, are used, Darwin tells us, for seizing the female, but they do not appear to be employed for this purpose in any other species. It might be held that they play the part of terrifying agents, as the eye-spots of Caterpillars72 and adult Lepidoptera are believed to do. At any rate, they seem to be so used in the case of a Beetle of South Chile (Chiasmognathus grantii) wherein the jaws are of great size and have their inner edges toothed. When threatened “he faces round, opens his great jaws, and at the same time stridulates freely.” But this parade of force is evidently no more than “bluffing,” for Darwin, who describes this behaviour, remarks, “the mandibles were not strong enough to pinch my finger so as to cause actual pain.” In the female, it may be remarked, the jaws are quite small.
That too much stress has been laid upon the significance 216of the enlarged jaws and other hypertrophied developments in the Beetles seems to be shown by the case of certain carnivorous Beetles, of which one species (Taphroderes distortus) may serve as an example. Herein the left jaw11 takes the form of a long, crooked74 strap-shaped outgrowth, whose purpose cannot even be conjectured75. And in this connection one may cite the case of certain species of Homoptera—Bugs—which occur in tropical South America. Here, in both sexes, as may be seen in Plate 40, Fig51. 4, the neck-shield is produced backwards76 far beyond the body, to form a most elaborate superstructure which appears to confound the most ingenious attempts at interpretation.
It is to be noted that wherever special structures are necessary for the performance of specific acts such as are of vital importance to the well-being77 of the race, they are developed to perfection: there is little or no variation in their size, and no doubt as to their purpose. Thus in many species means are necessary to enable the male to seize and hold the female during the sexual embrace. In the Water Beetle of our ponds and ditches (Dytiscus marginalis) the male bears a very remarkable sucker on each fore-leg, the adhesive79 surface of which, under the microscope, reveals an extraordinary complexity80 and wondrous81 beauty. This sucker forms a very conspicuous “secondary sexual character,” and is used in embracing his mate, whose back is deeply grooved82 to enhance the hold of the suckers. In some species punctures83 take the place of grooves84. Suckers, like those of Dytiscus are met with again in a Wasp85 (Crabro cribrarius). In another genus of Beetles (Penthe) cited by Darwin, the antenn? of the male have a few of the middle joints87 dilated88 and their under surfaces furnished 217with a cushion of hairs to aid in the sexual embrace.
Beetles are creatures of solitary89 habits; how, then, do they find their mates when, by the insistence90 of the reproductive desires, they are driven forth91 to begin the search? Though we have no direct evidence, it seems more than probable that, as with the Butterflies and Moths, scent furnishes their most reliable guide. At any rate, in a large number of species, as among the Lamellicornia, the antenn? bear leaf-like plates, which are much more developed in the males, in which they probably serve as scent-detecting organs.
In some species stridulating organs occur such as are met with in even greater perfection among the Crickets and Grasshoppers, and among the Spiders and Scorpions92. That these “musical-boxes” provide a means of communication between the sexes there can be no doubt, even if, as some contend, they are commonly used only to frighten enemies. This purpose may well be the explanation of their presence in the larval Stag Beetle, for it cannot be claimed that they have any relation to the acts of courtship at this stage of development.
Stridulating organs, wherever they are met with, are fashioned on the same principle. The mechanism93 for sound-production differs conspicuously from that which produces the voice in the vertebrates. For where there are no lungs or breathing apparatus94, comparable to that of birds and beasts, there can be no internal voice-mechanism. Instead, the skeleton which in these creatures forms the external surface of the body—that is to say, it encloses the muscles, whereas in the vertebrates it is internal and overlain by the muscles—produces the necessary sounds. And this by means of rubbing two opposed surfaces against 218one another, one of which is ridged, the other toothed. In the details both of position and structure a wonderful variety will be discovered when all the known types are surveyed, and it is possible that they perform different functions in different groups.
The Locusts and Grasshoppers are among the finest performers of these “harpists,” and it would seem that in this group, at any rate, the music they make is of an erotic character. In one of our native Grasshoppers (Stenobothrus melanopterus) these high-pitched and somewhat strident notes are produced by rubbing the roughened inner surface of the hindmost thigh96, which forms the base of the great leaping leg, against one of the libs of the wing-case which is specially27 enlarged and has a sharp edge. Thereby97 the wing is thrown into a state of vibration98 and the musical sound produced. The roughening of the inner surface of the thigh just referred to is produced by a row of bead-like projections99 whose appearance under the microscope is depicted100 in the adjoining illustration. This apparatus is well developed in the males, and but feebly, or not at all, in the females. That the music it produces is appreciated by the performers and their mates there can be no doubt, for they are provided with a special apparatus which fulfils the purpose of an ear. In the short-horned Grasshoppers (Acridiid?) this is placed in the middle of the body just above the base of the great thigh. It differs in the details of its construction. In some cases it is formed by a delicate sheet of membrane101 surrounded by a rim102, in others the membrane may be slightly depressed103, and in some very much so, the rim closing up to form a broad slit104. Such ears, it is to be noted, exist in both sexes, while the stridulating organs do not. That such sound-producing organs serve as stimulants105 to the sexual passions of the 219females is but a natural inference. Some authorities, however, regard this as doubtful, since there are species which appear to lack these stridulating instruments, though possessing ears. But closer observation will probably show that these apparently dumb species are not really so, as Dr. David Sharp, commenting on this fact remarks: “It is well known that sounds inaudible to some human ears are perfectly106 distinct to others. Tyndall, in his work on Sound, has illustrated107 this by a fact that is of special interest from our present point of view. ‘Crossing the Wengern Alp with a friend’ he says, ‘the grass on each side of the path swarmed108 with insects which, to me, rent the air with their shrill109 chirruping. My friend heard nothing of this, the Insect world lying beyond his limit of audition110!’ If human ears are so different in their capacity for perceiving vibrations111, it of course becomes more than probable that auditory organs so differently constituted as are those of insects from our own may hear sounds when the best human ear can detect nothing audible. On the whole, therefore, it would appear most probable that the Orthoptera provided with acoustic112 organs, and which we consider dumb, are not really so, but produce sounds which we cannot hear, and do so in some manner unknown to us. If this be the case, it is probable that these ears are special organs for hearing particular sounds.”
Plate 32.
STRIDULATING ORGANS. ETC.
2. The stridulating apparatus of a Grasshopper5—highly magnified.
4. The “ear” of a Grasshopper.
[Face page 218.
Certain of the Grasshoppers of Africa, known to entomologists as Pneumorides, have undergone a most extraordinary transformation113 of their bodily shape, as if in response to the demands of these musical performances. They have entirely114 lost the power of leaping, and the abdomen115, in the male, has become transformed into a 220huge, pellucid116, inflated117 bag or bladder, apparently to serve the purpose of a resonator, increasing the volume of the sound produced by the stridulating organ, which consists of a series of ridges118 placed on each side. The noise which this mechanism produces is, as might be supposed, considerable. It is curious to remark that in this group the females are more vividly119 coloured than the males. In the case of one South African species—Pneumora scutellaris—this coloration is so extravagant120 that she has been said to look as if “got up” for a fancy-dress ball (Plate 33, Fig. 1). Her ground colour is of a light green, with pearly-white markings, surrounded by an edging of magenta121; the white areas are very numerous. The face has magenta patches, and numerous, tiny, pearly-white tubercles, each of which, when placed on a green part, is surrounded by a ring of mauve. This scheme of coloration distinguishes her as one of the most remarkably122 coloured of insects. But to what are we to attribute these hues123? Sexual Selection will not explain them, and it seems unreasonable124 to regard them either as affording a protective or a warning coloration. They may then, perhaps, be allowed to rank as another instance of unchecked variation in the direction of vivid colouring, such as has been already described as occurring both among birds and other animals lower in the scale.
Plate 33.
CRICKETS AND MAY FLIES.
1 and 2 afford illustrations of the excessive development of “ornament “; fig. 3 of devices for seizing the female; figs125. 4 and 5 of unaccountable differences in the development of wings.
1. The Pneumatic Cricket (Pneumora scutellaris), showing the strange markings on the female.
3. The Giant Alder-fly (Corydalis crassicornis), with its huge jaws for grasping the female.
4. The Stone-fly (Perla maxima), the large-winged Continental128 form.
5. Loch Tanna Stone-fly (Isogenus nubecula), male, with vistigial wings.
[Face page 220.
In the Locustid? the ear is placed on the side of the front leg and the rim surrounding it may either take an oval shape or close up to form a slit. The air necessary for the efficient action of the acoustic apparatus is admitted through a gaping129 hole in the side of the body, above the base of the leg, an arrangement not met with among any other insects. The musical apparatus of these insects differs from that of the Acridiid?, for it is formed only by the wing-cases, and not by the wing 221case and the leg. One of the wings bears a file on its inner surface, the other, the right wing, is furnished with a sharp edge placed on a prominent part of its inner margin78. By slightly tilting130 the fore-wings, or wing-cases, and vibrating them rapidly, the edge passes under the file and a musical sound is produced. By this means one of our native long-horned Grasshoppers (Locusta viridissima) produces a shrill, but not unpleasant, sound, capable of being sustained continuously for a quarter of an hour. But a species encountered by Bates during his travels in the Amazons is a much more efficient performer. Known by the name of Tanana by the natives, it is so much admired by them for its singing powers that it is kept in little cages as we keep Canaries. That these organs are of importance to the species may be gathered from the case of a Bulgarian long-horned or Green Grasshopper (Poecilimon affinis), wherein the wings have so degenerated131 as to be useless in flight, but in the male they have been retained solely132 as musical instruments. In some species both sexes have a music-producing apparatus, but as a rule this is present only in the male.
That these curious and complex stridulating organs do indeed primarily act as aphrodisiacs seems to have been clearly demonstrated by the naturalist133 Bates, who, in speaking of the European Field Cricket remarks: “The male has been observed to place himself at the entrance to his burrow126, and stridulate until a female approaches, when the louder notes are succeeded by a more subdued134 tone, whilst the successful musician caresses135 with his antenn? the mate he has won.”
Among the most efficient and most celebrated136 performers of all on these instruments of percussion137 are 222the “Katydids” of North America. The sounds they produce are said to form the words “Katy-did, O-she-did, Katy-did-she-did.” The first of these extraordinary concerts is heard about mid-July; by mid-August they are in full song. By others the sounds have been likened to those produced by the slow turning of a child’s rattle138, ending in a sudden jerk; and this prolonged rattling139, which is peculiar140 to the male, is always answered by a single, sharp “chirp” or “tschick” from one or more females, who produce the sound by a sudden upward jerk of the wings.
Pride of place, however, among insect performances of this kind must surely be awarded to the Cicadas, which are notoriously the noisiest members of the Insect world, far eclipsing the shrill calls of the Grasshoppers and even of the Crickets. Darwin remarks that the noise they made could “be plainly heard on board the Beagle when anchored off Brazil at a quarter of a mile from the shore; and Captain Hancock says it can be heard at a distance of a mile. The Greeks formerly141 kept, and the Chinese now keep, these insects in cages for the sake of their song, so that it must be pleasing to the ears of some men.” Only the males sing, the females being completely dumb, and this prompted the Greek poet Xenarchus to make the now famous remark, “Happy the Cicadas’ lives, for they have voiceless wives.” Another naturalist, Riley, says: “The general noise, on approaching the infested142 woods, is a combination of that of a distant threshing-machine and a distant frog-pond.” Another species, Tympanoterpes gigas, also Brazilian, is said to make a noise equal to the whistle of a locomotive: recalling that of a nest of young snakes, or young birds, when disturbed—a sort of scream. They can also produce a 223chirp like that of a Cricket and a very loud, shrill screech143 prolonged for fifteen or twenty seconds, gradually increasing and decreasing in force.
Curiously enough, no special auditory organs have yet been discovered, and it has been suggested that these insects do not hear in our sense of the word, but feel rhythmical144 vibrations. But whether the males “sing in rivalry,” as Dr. David Sharp suggests, is another matter. The purpose of the “song” in the first place is no doubt intended as a guide to the females seeking mates. But it is quite conceivable that the call of one male may stimulate145 every other male in the neighbourhood. Darwin, commenting on this aspect of the music, gives a quotation146 from Dr. Hertman, who says: “The drums are now ... heard in all directions. This I believe to be the marital147 summons from the males. Standing in thick chestnut sprouts148 about as high as my head, where hundreds were around me, I observed the females coming around the drumming males.... This season a dwarf149 pear-tree in my garden produced about fifty larv? of Cicada pruinosa; and I several times noticed the females alight near a male while he was uttering his clanging notes.”
The structures, he remarks, from which these sounds proceed, “must be ranked amongst the most remarkable voice-organs in the animal kingdom. They are totally different from the stridulating organs that are found in many other insects.... Some difference of opinion has existed as to the manner in which the structures act, but the account given by Carlet ... will, we believe, be found to be essentially150 correct.” They are partly thoracic and partly abdominal151. On examining a male Cicada there will be seen, on the under surface, two plates, meeting in the middle line of the body and 224overlapping the base of the abdomen. They can be slightly moved away from the abdomen, and thereby a wide fissure152 will be produced, displaying the mechanism beneath. If the whole operculum be removed, three membranes153 will be seen, an external, called the “timbal,” an anterior154 folded and soft membrane, and a posterior “mirror.” This last is a very beautiful object, tensely stretched and pellucid, yet reflecting all the hues of the rainbow. The sound is primarily produced by the vibrations of the timbal, to which a muscle is attached; the other membranes are probably also set vibrating, and the whole skeleton helps to increase or modify the sound, which is probably also influenced by the position of the operculum, which varies in different species. A further control of the tension of the air is exerted by “stigmata” or pores, and certain air-chambers connected therewith.
Throughout these pages comment has been made on the apparently “fortuitous” character of complex patterns and structures. The “musical-box” of the Cicada affords yet another instance. Nevertheless there is an impressive harmony between the several parts; an interdependence which is not fortuitous. There is obviously a nexus155 of growth-controlling factors preserving harmony between each separate part which as yet has escaped all endeavour to discover.
While it is difficult to picture the initial stages of growth of so complex an organ as that of the Cicada, the beginnings of simpler structures such as the stridulating organs of Beetles and Grasshoppers are more easily discernible. “It is probable,” remarks Darwin, “that the two sexes of many kinds of Beetles were at first enabled to find each other by the slight shuffling156 noise produced by the rubbing together of the adjoining hard parts of their 225bodies; and that as those males or females which made the greatest noise succeeded best in finding partners, rugosities on various parts of their bodies were gradually developed by means of sexual selection into true stridulating organs.”
Structures to which we can ascribe a use are commonly supposed to have been evolved for the purpose which we assign to them. The “horns” of Beetles afford a case in point; but there are many other equally remarkable and extravagant developments among the insects which seem to defy explanation. And they will continue to do so until it is realized that they are but exaggerations of the normal processes of growth, which is not limited to definite areas but may produce extensions and excrescences of an almost infinitely157 varied158 character. The only controlling factor is that imposed by Natural Selection when these growth-changes tend to impair159 the well-being of the organism as a whole. Often such changes confer benefits, giving rise to new organs, and in this case Natural Selection encourages the new departure. Nothing, indeed, “succeeds like success.” New departures in one direction may be promptly160 suppressed, in another they spell fortune: there is no “Socialism” in Nature. Often these “new departures” neither help nor hinder, and instances of this kind are commonly afforded by “ornaments.” One of the most singular illustrations of this kind is furnished by that extraordinary Long-horned Grasshopper of India (Schizodactylus monstrosus), wherein the wings, when at rest, have their tips coiled up like a watch-spring, while the appendages161 to the legs are scarcely less remarkable. It is a burrower162, driving long tunnels in the banks of rivers. But little is known of its habits, save that it does not emerge from its burrow till night, when it takes long flights. This being 226so, the bizarre character of its wings and legs is the more difficult to explain on any Sexual Selection theory. But regarded as spontaneous variations which have not fallen under the ban of Natural Selection, they are somewhat less puzzling, though, having regard to the extraordinary transformation which the burrowing Mole-cricket and the allied Cylindrodes have undergone, in adaptation to fossorial habits, the legs of this insect are remarkable indeed.
While there can be no doubt that the musical performances of the Crickets and Locusts play an important part in courtship, in some of the Long-horned Locusts, at any rate, the males fight furiously when mate-hunting, and to this end the head and jaws are greatly enlarged. During the progress of the duel8 the wings are extended and held erect163, which is hardly what one would have expected, since in this position they would seem to be more exposed to danger.
All the insects so far surveyed have been more or less conspicuous for their vivid hues, yet in none of these have elaborate “displays” been recorded. To find demonstrativeness of this kind one must turn apparently to a group of minute, lowly organized, dull-coloured, wingless insects with ugly misshapen heads and bodies. The sexes do not differ in appearance, but they are interesting on account of the sedulous164 court which the males pay to the females. The late Lord Avebury, in a Communication to the Linnean Society, remarked of them: “It is very amusing to see these little creatures (Smynthurus luteus) coquetting together. The male, which is much smaller than the female, runs round her, and 227they butt14 one another, standing face to face and moving backwards and forwards like two playful lambs. Then the female pretends to run away and the male runs after her. With a queer appearance of anger, he gets in front and stands facing her again; then she turns coyly round, but he, quicker and more active, scuttles165 round too, and seems to whip her with his antenn?; then for a bit they stand face to face, play with their antennas166 and seem to be all in all to one another.”
The Dragon-flies are among the most beautiful of insects; they are also relatively167 long-lived, and they are conspicuous. Yet this beauty must be attributed to some inherent inward grace rather than to the ?sthetic instincts of the female. Moreover, in the matter of size and beauty there is little to choose between the sexes; where any difference occurs the males have the advantage. Though the mode of copulation is well known, nothing has been discovered as to the means whereby male and female discover one another. It is doubtful whether this can be done by sight, for with all the beauty of their shimmering168 suits of mail and gauzy wings, their vision is limited to a field of a few inches. Possibly scent is their guide; at any rate, dead Dragon-flies have a vile169 odour.
It is worth noting that there are no wingless Dragon-flies, and that none have developed unnecessary ornament in the form of spines170, horns, or frills of any kind, such as are so commonly met with among groups of more sedentary habits like the Phasmid? and the Beetles, for example. In other words, there is clearly a direct relation between ornament and the mode of life. It is also clear that some modes of subsistence are very inelastic, allowing of no more than very slight structural171 variations, for the Dragon-flies are an extremely ancient group. Fossil species of large size are known from the Lower Lias, and the remains172 228of a giant measuring two feet in expanse of wings has been found in the Carboniferous. This species, however, seems to have stood near the parting of the ways between the May-flies and the Dragon-flies. But be this as it may, undoubtedly173 Dragon-flies hovered174 over the backs of sleeping Ichthyosaurs and furnished food for Pterodactyles millions of years ago, as they now hover175 over lazy kine for the sake of the flies forgathered there, or dodge176 to avoid the stoop of the Hobby, and in all this vast space of time they have not appreciably177 changed.
And what is true of the Dragon-fly is true also of the May-fly, for it is clear that they are of the same stock. It is true at any rate in so far as the conformation of the body is concerned. The possibility that it may be equally true in regard to the details of their life-history almost staggers one, because these are, in many respects, of a quite remarkable character. As with the Dragon-fly, there is a prolonged period of larval life, lasting178 from one to two years, which time is passed in streams and pools where a luxuriant vegetation ensures a plentiful179 supply of food. Some are carnivorous, but in the majority of species minute plants only are eaten. More than forty species are to be reckoned as natives of the British Islands, the commonest being the “Green Drake” and “Grey Drake,” beloved by the fisherman. These names are applied, it may be mentioned, to the phase known as the sub-imago which precedes the fully-adult stage, of Ephemera vulgata and E. danica.
Save that it is curious that while the larv? of some species are carnivorous those of others are vegetarians180, there is nothing very remarkable about what may be called the infantile period. But when this is ended the 229span of life remaining to them as adults is brief indeed. Instinctively181 realizing that the time of transfiguration is at hand, the erstwhile crawling grub rises to the surface of the stream, and almost in the twinkling of an eye it mounts into the air on gauzy wings, there for a brief space to execute an aerial dance which in its every phase is amazing. Some species never see the sun. They emerge as the sky begins to redden, and as its glory fades they, too, expire. This brief space is all that Nature has allowed them in which to fulfil her behest to all living things—to increase and multiply. And myriads182 die without even a chance to effect this consummation of existence.
The dance is a Dance of Death, and it is performed by a host so vast as to surpass the bounds of belief save to those who have had the good fortune to witness a scene so amazing.
D’Albertis tells of a gathering183 which he witnessed on the Fly River, New Guinea—for these insects have a world-wide distribution—wherein countless184 myriads were assembled. “For miles the surface of the river, from side to side, was white with them as they hung over it on gauzy wings; at certain moments, obeying some mysterious signal, they would rise in the air and then sink down anew like a fall of snow.” And in this assemblage he estimated that there was but one female to every five or six thousand males. It is during this flight that the act of mating is performed. The fortunate male from the host of rivals, in this mid-air embrace is aided by the foremost pair of legs, which are especially curved to effect this purpose. The embrace is momentary185. Thereafter he dies; to the female a somewhat longer span of life remains, for she has yet to deposit her eggs, and 230this being done en masse, she, too, expires.
It is curious that these creatures, which in their winged state have never seen the sun, should be attracted by light. But such is the case. I well remember witnessing an instance of this years ago, while staying, one August, at Bingen on the Rhine. Dinner was served in the open air, and just as the soup was served May-flies in myriads swarmed round the lamps and fell on the tables as thick as snow-flakes. Some of these were in copula, and I succeeded in bottling a few specimens186 for the British Museum, where they still remain to remind me of this amazing scene.
About three hundred species of May-flies are known, and some enjoy a somewhat longer span of life than others. In no case, however, do they emerge till just before sunset; but in some species it is believed life may be prolonged for as much as three or four days, or even longer, if the weather be cold and wet, so as to keep them in a state of enforced rest, which amounts to a state of coma187.
That their hold on life during this final stage of existence is brief there can be no gainsaying188, for it is passed fasting. Jaws are wanting, and the whole alimentary189 canal has been transformed into one long air-chamber. Its walls are now of extreme tenuity, and by changes in the interior of the tube, valves are formed which convert the stomach into a capacious air-sac.” When movements,” remarks Dr. David Sharp, “tend to increase the capacity of the body cavity then air enters into the stomachic sac by the mouth orifice, but when muscular contractions190 result in pressure on the sac they close the orifices of its extremities191 by the valve-like structures just referred to; the result is, that as the complex movements of the body are made the stomach becomes more 231and more distended192 by air.” It was known even to the old naturalists193 that the dancing May-fly is a sort of balloon, but they were not acquainted with the exact mode of inflation. Palmen says that in addition to the valve-like arrangements we have described, the entry into the canal is controlled by a circular muscle with which are connected radiating muscles attached to the walls of the head. The canal thus strangely transformed performs the functions of a balloon, and at the same time aids the functions of the reproductive organs.
Where vast numbers of individuals set out simultaneously194 to achieve their nuptials196 there would seem to be no need for special devices on the part of either sex to call attention to their whereabouts. Nevertheless, it is highly probable that the female exhales197 some distinctive198 odour; otherwise, having regard to the fact that she is overwhelmingly outnumbered by suitors, her discovery in such a crowd would be impossible, and it is of vital importance that no time should be lost in effecting conjugation, for the time for its accomplishment199 is perilously200 short. But there is another possible means of discrimination—the males may distinguish the females by the very different appearance of the head in the latter. At any rate, this may be true of some species wherein the males have no less than seven eyes, and these of three different kinds! The compound eyes, characteristic of insects, are, in these, divided, one half being set upon the summit of a pillar raised high above the level of the head, the other part remaining in its normal place at the side of the head; and in front of these, on what may be called the forehead, are three separate simple eyes, or “ocelli.” A reference to Plate 32, Fig. 3, will make this clear.
That the history of the later life of the May-fly is 232remarkable no one will deny: in many respects it is unique. Yet for all its strangeness it enables us to set our compasses, so to speak, in regard to the phenomena201 of sex in other groups. The extraordinary disparity in the proportions between male and female, for example, is full of significance, for it shows, as has been suggested more than once in these pages, that, in the case of polygamous species, we are probably in error in supposing that the excess of females is due to the reduction in the number of males by reason of the elimination202 of males by fighting. The excess of males, or females, as the case may be, is due to an inherent quality in the germ-plasm. The May-fly might be regarded as an excessively polyandrous species if the number of males in relation to females alone be regarded: but actually it is monogamous. After a prosaic203 infancy204 they are suddenly transformed into gay lovers, dancing a marriage-dance. But for them is no marriage feast, nor any later sequence of domesticity. One in ten thousand may find a mate, and only in this is he more fortunate than his neighbours, for, like them, he too must die before the dawn. Theirs is not even a sleep and a forgetting, but “one splendid hour of Life, and then—oblivion.” It may be urged that even these which might seem to have been fooled, have not really lived in vain, for hosts of animals feast upon their bodies. Myriads, indeed, are snapped up by fishes even before they have opened their wings, while birds rudely invade the swarms205 as they dance in mid-air, feasting on these fasting ones. But this is, after all, an inglorious end, and leaves us still asking Cui bono?
Is this amazing life-history a thing of yesterday, a new phase, or an order of things as old as the origin of the species, dating back some millions of years?
233So far as one can profitably speculate on such a theme it would seem more likely to be a relatively recent innovation. The nearly-related Alder-flies (Sialid?), so well known to anglers, seem like to meet with a similar fate, for the female lives but for a few days only and the male has an even briefer existence as a winged insect. The family to which the Alder-flies belong contains a few species which attain37 gigantic proportions, as, for example, in the case of the North American members of the genus Corydalis, which are giants. The males thereof are remarkable for the fact that they are armed with enormous jaws, which may be likened to a pair of callipers whose limbs have been crossed. These weapons serve as claspers, enabling the males to seize and hold the females during the act of mating. But even here the same brief span of life has to suffice them, for death follows swiftly on the fulfilment of the nuptial195 rites206.
The Perlid?, or Stone-flies, which, like the Sialid?, are aquatic207 Neuroptera, the larval stages being passed in streams, present very puzzling features in regard to the adult males which, so far, have baffled all attempts at solution; yet they seem to have a very important bearing on the all-important work of reproduction. They are among the earliest insects to appear in spring, and possess an extraordinary power of resisting cold. One species, Capina vernalis, common in the Albany River, in Canada, frequently comes up through cracks in the ice and casts its skin there! Another, Nemoura glacialis, which appears at about the same time, actually performs the nuptial rites in crevices208 in the dissolving ice! Happily reason is denied them, or they would find life a mockery indeed; for having attained their final development, when the joyous209 and exhilarating exercise of 234flight should be theirs, they are compelled forthwith to fulfil their reproductive functions and die—in an ice-chamber! The males have wings which are rarely or never unfurled; as a rule they present nothing more than a crumpled210 mass of gauzy tissue, as if glued together. Such species as attain to flight are most indifferent performers, travelling but slowly, with laboured movements and settling after a few yards have been traversed.
As a rule, among insects, where there is a difference in the power of flight, it is the male which is superior. The case of Nemoura, just referred to, affords an instance where the contrary is the case, and Mr. J. J. Lister records the case of one of these flies—Isogenus nubecula—taken at Loch Tanna in Arran, wherein the wings of the female were greatly reduced, while those of the male were so much so as to be mere211 useless vestiges212. Similar facts have been recorded of more than one species in Scotland, but in all such cases the phenomenon seems to be associated with the appearance of the insect in very early spring. In another species—Nemoura trifasciata—only the front wings are reduced, the hind95 pair being large enough to cover the body. In male specimens of Perla maxima taken in Scotland, the wings are so short as to be useless for the purposes of flight, yet, in the same species taken in Central Europe, they are of ample proportions.
These facts are puzzling indeed, but they seem to show that flight is not essential to attain the ends of reproduction. As to whether these flies secure their mates by any kind of “courtship,” or how they find one another, seems not to be known. But the female is remarkable for the fact that she carries her eggs about with her, to the number of five or six thousand, attached to the 235end of the abdomen.
Having regard to the fact that three thousand species of Perlid? are known, and that they have a wide distribution over the earth’s surface, one might have expected that more would be known of their singular life-history. They are, however, flies of very unattractive appearance and great frailty213, hence, save to anglers, by whom they are esteemed214 as bait for trout215, they attract but little attention.
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1
ornament
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| v.装饰，美化；n.装饰，装饰物 | |
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2
beetles
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| n.甲虫( beetle的名词复数 ) | |
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3
beetle
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| n.甲虫，近视眼的人 | |
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4
grasshoppers
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| n.蚱蜢( grasshopper的名词复数 )；蝗虫；蚂蚱；（孩子）矮小的 | |
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5
grasshopper
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| n.蚱蜢，蝗虫，蚂蚱 | |
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6
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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7
locusts
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| n.蝗虫( locust的名词复数 )；贪吃的人；破坏者；槐树 | |
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8
duel
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| n./v.决斗；(双方的)斗争 | |
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duels
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| n.两男子的决斗( duel的名词复数 )；竞争，斗争 | |
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10
jaws
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| n.口部；嘴 | |
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jaw
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| n.颚，颌，说教，流言蜚语；v.喋喋不休，教训 | |
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12
conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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13
dictate
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| v.口授；(使)听写；指令，指示，命令 | |
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14
butt
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| n.笑柄；烟蒂；枪托；臀部；v.用头撞或顶 | |
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15
moths
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| n.蛾( moth的名词复数 ) | |
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16
illustrate
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| v.举例说明，阐明；图解，加插图 | |
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17
scent
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| n.气味，香味，香水，线索，嗅觉；v.嗅，发觉 | |
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18
exquisitely
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| adv.精致地；强烈地；剧烈地；异常地 | |
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19
interpretation
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| n.解释，说明，描述；艺术处理 | |
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20
judgment
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| n.审判；判断力，识别力，看法，意见 | |
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21
misgivings
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| n.疑虑，担忧，害怕；疑虑，担心，恐惧( misgiving的名词复数 )；疑惧 | |
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22
biased
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| a.有偏见的 | |
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23
stimulus
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| n.刺激，刺激物，促进因素，引起兴奋的事物 | |
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24
postulating
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| v.假定，假设( postulate的现在分词 ) | |
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applied
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| adj.应用的；v.应用，适用 | |
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26
dominant
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| adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因 | |
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27
specially
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| adv.特定地；特殊地；明确地 | |
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28
tinted
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| adj. 带色彩的 动词tint的过去式和过去分词 | |
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29
brilliance
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| n.光辉，辉煌，壮丽，（卓越的）才华，才智 | |
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30
parental
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| adj.父母的；父的；母的 | |
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31
intensification
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| n.激烈化，增强明暗度；加厚 | |
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32
pigment
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| n.天然色素，干粉颜料 | |
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33
relegated
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| v.使降级( relegate的过去式和过去分词 )；使降职；转移；把…归类 | |
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34
ornaments
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| n.装饰( ornament的名词复数 )；点缀；装饰品；首饰v.装饰，点缀，美化( ornament的第三人称单数 ) | |
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35
crests
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| v.到达山顶（或浪峰）( crest的第三人称单数 )；到达洪峰，达到顶点 | |
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36
impelled
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| v.推动、推进或敦促某人做某事( impel的过去式和过去分词 ) | |
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37
attain
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| vt.达到，获得，完成 | |
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attained
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| （通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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39
laboriously
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| adv.艰苦地；费力地；辛勤地；（文体等）佶屈聱牙地 | |
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40
touching
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| adj.动人的，使人感伤的 | |
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41
prominences
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| n.织物中凸起的部分；声望( prominence的名词复数 )；突出；重要；要事 | |
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42
downwards
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| adj./adv.向下的（地），下行的（地） | |
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43
chestnut
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| n.栗树，栗子 | |
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44
triangular
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| adj.三角（形）的，三者间的 | |
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45
ledge
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| n.壁架，架状突出物；岩架，岩礁 | |
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46
reindeer
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| n.驯鹿 | |
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47
curiously
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| adv.有求知欲地；好问地；奇特地 | |
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48
allied
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| adj.协约国的；同盟国的 | |
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49
friction
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| n.摩擦，摩擦力 | |
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50
conjecture
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| n./v.推测，猜测 | |
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51
fig
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| n.无花果(树) | |
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52
habitual
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| adj.习惯性的；通常的，惯常的 | |
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53
fixedly
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| adv.固定地；不屈地，坚定不移地 | |
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54
standing
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| n.持续，地位；adj.永久的，不动的，直立的，不流动的 | |
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55
amphibians
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| 两栖动物( amphibian的名词复数 )； 水陆两用车； 水旱两生植物； 水陆两用飞行器 | |
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56
apparently
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| adv.显然地；表面上，似乎 | |
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57
crux
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| adj.十字形；难事，关键，最重要点 | |
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58
eccentricities
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| n.古怪行为( eccentricity的名词复数 )；反常；怪癖 | |
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59
discredited
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| 不足信的，不名誉的 | |
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machinery
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| n.(总称)机械，机器；机构 | |
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61
incipient
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| adj.起初的，发端的，初期的 | |
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62
penalizes
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| 对…予以惩罚( penalize的第三人称单数 )； 使处于不利地位 | |
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63
beak
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| n.鸟嘴，茶壶嘴，钩形鼻 | |
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64
thumped
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| v.重击， （指心脏）急速跳动( thump的过去式和过去分词 ) | |
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65
vanquished
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| v.征服( vanquish的过去式和过去分词 )；战胜；克服；抑制 | |
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66
noted
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| adj.著名的，知名的 | |
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67
severely
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| adv.严格地；严厉地；非常恶劣地 | |
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68
pretensions
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| 自称( pretension的名词复数 )； 自命不凡； 要求； 权力 | |
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69
pugnacity
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| n.好斗，好战 | |
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conspicuously
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| ad.明显地，惹人注目地 | |
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71
semblance
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| n.外貌，外表 | |
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72
caterpillars
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| n.毛虫( caterpillar的名词复数 )；履带 | |
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73
gnat
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| v.对小事斤斤计较，琐事 | |
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74
crooked
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| adj.弯曲的；不诚实的，狡猾的，不正当的 | |
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75
conjectured
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| 推测，猜测，猜想( conjecture的过去式和过去分词 ) | |
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76
backwards
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| adv.往回地，向原处，倒，相反，前后倒置地 | |
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77
well-being
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| n.安康，安乐，幸福 | |
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78
margin
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| n.页边空白；差额；余地，余裕；边，边缘 | |
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79
adhesive
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| n.粘合剂；adj.可粘着的，粘性的 | |
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80
complexity
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| n.复杂(性)，复杂的事物 | |
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81
wondrous
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| adj.令人惊奇的，奇妙的；adv.惊人地；异乎寻常地；令人惊叹地 | |
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82
grooved
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| v.沟( groove的过去式和过去分词 )；槽；老一套；（某种）音乐节奏 | |
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83
punctures
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| n.（尖物刺成的）小孔( puncture的名词复数 )；（尤指）轮胎穿孔；（尤指皮肤上被刺破的）扎孔；刺伤v.在（某物）上穿孔( puncture的第三人称单数 )；刺穿（某物）；削弱（某人的傲气、信心等）；泄某人的气 | |
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84
grooves
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| n.沟( groove的名词复数 )；槽；老一套；（某种）音乐节奏v.沟( groove的第三人称单数 )；槽；老一套；（某种）音乐节奏 | |
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85
wasp
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| n.黄蜂，蚂蜂 | |
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86
crab
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| n.螃蟹，偏航，脾气乖戾的人，酸苹果；vi.捕蟹，偏航，发牢骚；vt.使偏航，发脾气 | |
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87
joints
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| 接头( joint的名词复数 )； 关节； 公共场所（尤指价格低廉的饮食和娱乐场所） （非正式）； 一块烤肉 （英式英语） | |
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88
dilated
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| adj.加宽的，扩大的v.（使某物）扩大，膨胀，张大( dilate的过去式和过去分词 ) | |
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89
solitary
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| adj.孤独的，独立的，荒凉的；n.隐士 | |
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90
insistence
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| n.坚持；强调；坚决主张 | |
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91
forth
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| adv.向前；向外，往外 | |
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92
scorpions
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| n.蝎子( scorpion的名词复数 ) | |
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93
mechanism
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| n.机械装置；机构，结构 | |
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94
apparatus
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| n.装置，器械；器具，设备 | |
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95
hind
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| adj.后面的，后部的 | |
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96
thigh
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| n.大腿；股骨 | |
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97
thereby
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| adv.因此，从而 | |
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98
vibration
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| n.颤动，振动；摆动 | |
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99
projections
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| 预测( projection的名词复数 )； 投影； 投掷； 突起物 | |
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100
depicted
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| 描绘，描画( depict的过去式和过去分词 )； 描述 | |
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101
membrane
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| n.薄膜，膜皮，羊皮纸 | |
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102
rim
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| n.(圆物的)边，轮缘；边界 | |
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103
depressed
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| adj.沮丧的，抑郁的，不景气的，萧条的 | |
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104
slit
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| n.狭长的切口；裂缝；vt.切开，撕裂 | |
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105
stimulants
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| n.兴奋剂( stimulant的名词复数 )；含兴奋剂的饮料；刺激物；激励物 | |
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106
perfectly
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| adv.完美地，无可非议地，彻底地 | |
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107
illustrated
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| adj. 有插图的，列举的 动词illustrate的过去式和过去分词 | |
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108
swarmed
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| 密集( swarm的过去式和过去分词 )； 云集； 成群地移动； 蜜蜂或其他飞行昆虫成群地飞来飞去 | |
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109
shrill
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| adj.尖声的；刺耳的；v尖叫 | |
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110
audition
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| n.(对志愿艺人等的)面试(指试读、试唱等) | |
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111
vibrations
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| n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动 | |
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112
acoustic
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| adj.听觉的，声音的；(乐器)原声的 | |
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113
transformation
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| n.变化；改造；转变 | |
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114
entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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115
abdomen
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| n.腹，下腹(胸部到腿部的部分) | |
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116
pellucid
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| adj.透明的，简单的 | |
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117
inflated
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| adj.（价格）飞涨的；（通货）膨胀的；言过其实的；充了气的v.使充气（于轮胎、气球等）( inflate的过去式和过去分词 )；（使）膨胀；（使）通货膨胀；物价上涨 | |
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118
ridges
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| n.脊( ridge的名词复数 )；山脊；脊状突起；大气层的)高压脊 | |
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119
vividly
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| adv.清楚地，鲜明地，生动地 | |
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120
extravagant
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| adj.奢侈的；过分的；(言行等)放肆的 | |
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121
magenta
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| n..紫红色（的染料）；adj.紫红色的 | |
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122
remarkably
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| ad.不同寻常地，相当地 | |
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123
hues
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| 色彩( hue的名词复数 )； 色调； 信仰； 观点 | |
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124
unreasonable
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| adj.不讲道理的，不合情理的，过度的 | |
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125
figs
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| figures 数字，图形，外形 | |
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126
burrow
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| vt.挖掘(洞穴)；钻进；vi.挖洞；翻寻；n.地洞 | |
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127
burrowing
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| v.挖掘（洞穴），挖洞( burrow的现在分词 )；翻寻 | |
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128
continental
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| adj.大陆的，大陆性的，欧洲大陆的 | |
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129
gaping
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| adj.口的；张口的；敞口的；多洞穴的v.目瞪口呆地凝视( gape的现在分词 )；张开，张大 | |
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130
tilting
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| 倾斜，倾卸 | |
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131
degenerated
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| 衰退，堕落，退化( degenerate的过去式和过去分词 ) | |
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132
solely
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| adv.仅仅，唯一地 | |
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133
naturalist
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| n.博物学家(尤指直接观察动植物者) | |
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134
subdued
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| adj. 屈服的，柔和的，减弱的 动词subdue的过去式和过去分词 | |
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135
caresses
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| 爱抚，抚摸( caress的名词复数 ) | |
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136
celebrated
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| adj.有名的，声誉卓著的 | |
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137
percussion
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| n.打击乐器；冲突，撞击；震动，音响 | |
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138
rattle
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| v.飞奔，碰响；激怒；n.碰撞声；拨浪鼓 | |
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139
rattling
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| adj. 格格作响的, 活泼的, 很好的 adv. 极其, 很, 非常 动词rattle的现在分词 | |
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140
peculiar
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|
| adj.古怪的，异常的；特殊的，特有的 | |
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141
formerly
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| adv.从前，以前 | |
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142
infested
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| adj.为患的，大批滋生的（常与with搭配）v.害虫、野兽大批出没于( infest的过去式和过去分词 )；遍布于 | |
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143
screech
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|
| n./v.尖叫；(发出)刺耳的声音 | |
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144
rhythmical
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| adj.有节奏的，有韵律的 | |
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145
stimulate
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| vt.刺激，使兴奋；激励，使…振奋 | |
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146
quotation
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| n.引文，引语，语录；报价，牌价，行情 | |
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147
marital
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| adj.婚姻的，夫妻的 | |
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148
sprouts
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| n.新芽，嫩枝( sprout的名词复数 )v.发芽( sprout的第三人称单数 )；抽芽；出现；（使）涌现出 | |
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149
dwarf
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| n.矮子，侏儒，矮小的动植物；vt.使…矮小 | |
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150
essentially
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| adv.本质上，实质上，基本上 | |
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151
abdominal
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| adj.腹（部）的，下腹的；n.腹肌 | |
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152
fissure
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| n.裂缝；裂伤 | |
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153
membranes
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| n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物 | |
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154
anterior
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| adj.较早的；在前的 | |
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155
nexus
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| n.联系；关系 | |
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156
shuffling
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| adj. 慢慢移动的, 滑移的 动词shuffle的现在分词形式 | |
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157
infinitely
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| adv.无限地，无穷地 | |
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158
varied
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| adj.多样的，多变化的 | |
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159
impair
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| v.损害，损伤；削弱，减少 | |
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160
promptly
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| adv.及时地，敏捷地 | |
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161
appendages
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| n.附属物( appendage的名词复数 )；依附的人；附属器官；附属肢体（如臂、腿、尾等） | |
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162
burrower
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| 借钱人； 借用人，剽窃者 | |
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163
erect
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| n./v.树立，建立，使竖立；adj.直立的，垂直的 | |
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164
sedulous
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| adj.勤勉的，努力的 | |
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165
scuttles
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| n.天窗( scuttle的名词复数 )v.使船沉没( scuttle的第三人称单数 )；快跑，急走 | |
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166
antennas
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| [生] 触角，触须（antenna的复数形式） | |
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167
relatively
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| adv.比较...地，相对地 | |
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168
shimmering
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| v.闪闪发光，发微光( shimmer的现在分词 ) | |
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169
vile
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| adj.卑鄙的，可耻的，邪恶的；坏透的 | |
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170
spines
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| n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊 | |
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171
structural
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| adj.构造的，组织的，建筑（用）的 | |
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172
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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173
undoubtedly
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| adv.确实地，无疑地 | |
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174
hovered
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| 鸟( hover的过去式和过去分词 )； 靠近（某事物）； （人）徘徊； 犹豫 | |
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175
hover
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| vi.翱翔，盘旋；徘徊；彷徨，犹豫 | |
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176
dodge
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| v.闪开，躲开，避开；n.妙计，诡计 | |
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177
appreciably
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| adv.相当大地 | |
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178
lasting
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| adj.永久的，永恒的；vbl.持续，维持 | |
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179
plentiful
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| adj.富裕的，丰富的 | |
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180
vegetarians
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| n.吃素的人( vegetarian的名词复数 )；素食者；素食主义者；食草动物 | |
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181
instinctively
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| adv.本能地 | |
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182
myriads
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| n.无数，极大数量( myriad的名词复数 ) | |
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183
gathering
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| n.集会，聚会，聚集 | |
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184
countless
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| adj.无数的，多得不计其数的 | |
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185
momentary
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| adj.片刻的，瞬息的；短暂的 | |
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186
specimens
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| n.样品( specimen的名词复数 )；范例；（化验的）抽样；某种类型的人 | |
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187
coma
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| n.昏迷，昏迷状态 | |
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188
gainsaying
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| v.否认，反驳( gainsay的现在分词 ) | |
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189
alimentary
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| adj.饮食的，营养的 | |
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190
contractions
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| n.收缩( contraction的名词复数 )；缩减；缩略词；（分娩时）子宫收缩 | |
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191
extremities
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| n.端点( extremity的名词复数 )；尽头；手和足；极窘迫的境地 | |
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192
distended
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| v.（使）膨胀，肿胀( distend的过去式和过去分词 ) | |
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193
naturalists
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| n.博物学家( naturalist的名词复数 )；（文学艺术的）自然主义者 | |
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194
simultaneously
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| adv.同时发生地，同时进行地 | |
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195
nuptial
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| adj.婚姻的，婚礼的 | |
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196
nuptials
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| n.婚礼；婚礼( nuptial的名词复数 ) | |
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197
exhales
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| v.呼出，发散出( exhale的第三人称单数 )；吐出（肺中的空气、烟等），呼气 | |
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198
distinctive
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| adj.特别的，有特色的，与众不同的 | |
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accomplishment
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| n.完成，成就，（pl.）造诣，技能 | |
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perilously
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| adv.充满危险地，危机四伏地 | |
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201
phenomena
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| n.现象 | |
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202
elimination
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| n.排除，消除，消灭 | |
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prosaic
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| adj.单调的，无趣的 | |
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204
infancy
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| n.婴儿期；幼年期；初期 | |
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205
swarms
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| 蜂群，一大群( swarm的名词复数 ) | |
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rites
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| 仪式，典礼( rite的名词复数 ) | |
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aquatic
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| adj.水生的，水栖的 | |
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208
crevices
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| n.（尤指岩石的）裂缝，缺口( crevice的名词复数 ) | |
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209
joyous
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| adj.充满快乐的；令人高兴的 | |
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210
crumpled
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| adj. 弯扭的, 变皱的 动词crumple的过去式和过去分词形式 | |
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mere
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| adj.纯粹的；仅仅，只不过 | |
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212
vestiges
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| 残余部分( vestige的名词复数 )； 遗迹； 痕迹； 毫不 | |
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213
frailty
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| n.脆弱；意志薄弱 | |
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214
esteemed
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| adj.受人尊敬的v.尊敬( esteem的过去式和过去分词 )；敬重；认为；以为 | |
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trout
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| n.鳟鱼；鲑鱼(属) | |
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