20 Use of the gaudy Colours of many Caterpillars

Since this essay was first published a very curious difficulty has been cleared up by the application of the general principle of protective colouring. Great numbers of caterpillars¹ are so brilliantly marked and coloured as to be very conspicuous³ even at a considerable distance, and it has been noticed that such caterpillars seldom hide themselves. Other species, however, are green or brown, closely resembling the colours of the substances on which they feed, while others again imitate sticks, and stretch themselves out motionless from a twig⁴ so as to look like one of its branches. Now, as caterpillars form so large a part of the food of birds, it was not easy to understand why any of them should have such bright colours and markings as to make them specially⁵ visible. Mr. Darwin had put the case to me as a difficulty from another point of view, for he had arrived at the conclusion that brilliant colouration in the animal kingdom is mainly due to sexual selection, and this could not have acted in the case of sexless larv?. Applying here the analogy of other insects, I reasoned, that since some caterpillars were evidently protected by their imitative colouring, and others by their spiny⁶ or hairy bodies, the bright colours of the rest must also be in some way useful to them. I further thought that as some butterflies and moths⁸ were greedily eaten by birds while others were distasteful to them, and these latter were mostly of conspicuous colours, so probably these brilliantly coloured caterpillars were distasteful, and therefore never eaten by birds. Distastefulness alone would however be of little service to caterpillars, because their soft and juicy bodies are so delicate, that if seized and afterwards rejected by a bird they would almost certainly be killed. Some constant and easily perceived signal was therefore necessary to serve as a warning to birds never to touch these uneatable kinds, and a very gaudy⁹ and conspicuous colouring with the habit of fully¹⁰ exposing themselves to view becomes such a signal, being in strong contrast with the green or brown tints¹¹ and retiring habits of the eatable kinds. The subject was brought by me before the Entomological Society (see Proceedings¹², March 4th, 1867), in order that those members having opportunities for making observations might do so in the following summer; and I also wrote a letter to the Field newspaper, begging that some of its readers would cooperate in making observations on what insects were rejected by birds, at the same time fully explaining the great interest and scientific importance of the problem. It is a curious example of how few of the country readers of that paper are at all interested in questions of simple natural history, that I only obtained one answer from a gentleman in Cumberland, who gave me some interesting observations on the general dislike and abhorrence¹³ of all birds to the “Gooseberry Caterpillar²,” probably that of the Magpie¹⁴-moth⁷ (Abraxas grossulariata). Neither young pheasants, partridges, nor wild-ducks could be induced to eat it, sparrows and finches never touched it, and all birds to whom he offered it rejected it with evident dread¹⁵ and abhorrence. It will be seen that these observations are confirmed by those of two members of the Entomological Society to whom we are indebted for more detailed¹⁶ information.

In March, 1869, Mr. J. Jenner Weir¹⁷ communicated a valuable series of observations made during many years, but more especially in the two preceding summers, in his aviary¹⁸, containing the following birds of more or less insectivorous habits:— Robin¹⁹, Yellow–Hammer, Reed-bunting, Bullfinch, Chaffinch, Crossbill, Thrush, Tree–Pipit, Siskin, and Redpoll. He found that hairy caterpillars were uniformly rejected; five distinct species were quite unnoticed by all his birds, and were allowed to crawl about the aviary for days with impunity²⁰. The spiny caterpillars of the Tortoiseshell and Peacock butterflies were equally rejected; but in both these cases Mr. Weir thinks it is the taste, not the hairs or spines²¹, that are disagreeable, because some very young caterpillars of a hairy species were rejected although no hairs were developed, and the smooth pup? of the above-named butterflies were refused as persistently²² as the spined²³ larv?. In these cases, then, both hairs and spines would seem to be mere²⁴ signs of uneatableness.

His next experiments were with those smooth gaily-coloured caterpillars which never conceal²⁵ themselves, but on the contrary appear to court observation. Such are those of the Magpie moth (Abraxas grossulariata), whose caterpillar is conspicuously²⁶ white and black spotted²⁷ — the Diloba coeruleocephala, whose larv? is pale yellow with a broad blue or green lateral²⁸ band — the Cucullia verbasci, whose larv? is greenish white with yellow bands and black spots, and Anthrocera filipendul? (the six spot Burnet moth), whose caterpillar is yellow with black spots. These were given to the birds at various times, sometimes mixed with other kinds of larv? which were greedily eaten, but they were in every case rejected apparently²⁹ unnoticed, and were left to crawl about till they died.

The next set of observations were on the dull-coloured and protected larv?, and the results of numerous experiments are thus summarised by Mr. Weir. “All caterpillars whose habits are nocturnal, which are dull coloured, with fleshy bodies and smooth skins, are eaten with the greatest avidity. Every species of green caterpillar is also much relished³⁰. All Geometr?, whose larv? resemble twigs³¹ as they stand out from the plant on their anal prolegs, are invariably eaten.”

At the same meeting Mr. A. G. Butler, of the British Museum, communicated the results of his observations with lizards³², frogs, and spiders, which strikingly corroborate³³ those of Mr. Weir. Three green lizards (Lacerta viridis) which he kept for several years, were very voracious³⁴, eating all kinds of food, from a lemon cheesecake to a spider, and devouring³⁵ flies, caterpillars, and humble³⁷ bees; yet there were some caterpillars and moths which they would seize only to drop immediately. Among these the principal were the caterpillar of the Magpie moth (Abraxas grossulariata) and the perfect six spot Burnet moth (Anthrocera filipendul?). These would be first seized but invariably dropped in disgust, and afterwards left unmolested. Subsequently frogs were kept and fed with caterpillars from the garden, but two of these — that of the before-mentioned Magpie moth, and that of the V. moth (Halia wavaria), which is green with conspicuous white or yellow stripes and black spots — were constantly rejected. When these species were first offered, the frogs sprang at them eagerly and licked them into their mouths; no sooner, however, had they done so than they seemed to be aware of the mistake that they had made, and sat with gaping³⁸ mouths, rolling their tongues about until they had got quit of the nauseous morsels³⁹.

With spiders the same thing occurred. These two caterpillars were repeatedly put into the webs both of the geometrical and hunting spiders (Epeira diadema and Lycosa sp.), but in the former case they were cut out and allowed to drop; in the latter, after disappearing in the jaws⁴⁰ of their captor down his dark silken funnel⁴¹, they invariably reappeared, either from below or else taking long strides up the funnel again. Mr. Butler has observed lizards fight with and finally devour³⁶ humble bees, and a frog sitting on a bed of stone-crop leap up and catch the bees which flew over his head, and swallow them, in utter disregard of their stings. It is evident, therefore, that the possession of a disagreeable taste or odour is a more effectual protection to certain conspicuous caterpillars and moths, than would be even the possession of a sting.

The observations of these two gentlemen supply a very remarkable⁴² confirmation⁴³ of the hypothetical solution of the difficulty which I had given two years before. And as it is generally acknowledged that the best test of the truth and completeness of a theory is the power which it gives us of prevision, we may I think fairly claim this as a case in which the power of prevision has been successfully exerted, and therefore as furnishing a very powerful argument in favour of the truth of the theory of Natural Selection.

1 caterpillars   

n.毛虫( caterpillar的名词复数 )；履带

参考例句：

• Caterpillars eat the young leaves of this plant. 毛毛虫吃这种植物的嫩叶。
• Caterpillars change into butterflies or moths. 毛虫能变成蝴蝶或蛾子。 来自辞典例句

2 caterpillar   

n.毛虫，蝴蝶的幼虫

参考例句：

• A butterfly is produced by metamorphosis from a caterpillar.蝴蝶是由毛虫脱胎变成的。
• A caterpillar must pass through the cocoon stage to become a butterfly.毛毛虫必须经过茧的阶段才能变成蝴蝶。

3 conspicuous   

adj.明眼的，惹人注目的；炫耀的，摆阔气的

参考例句：

• It is conspicuous that smoking is harmful to health.很明显，抽烟对健康有害。
• Its colouring makes it highly conspicuous.它的色彩使它非常惹人注目。

4 twig   

n.小树枝，嫩枝；v.理解

参考例句：

• He heard the sharp crack of a twig.他听到树枝清脆的断裂声。
• The sharp sound of a twig snapping scared the badger away.细枝突然折断的刺耳声把獾惊跑了。

5 specially   

adv.特定地；特殊地；明确地

参考例句：

• They are specially packaged so that they stack easily.它们经过特别包装以便于堆放。
• The machine was designed specially for demolishing old buildings.这种机器是专为拆毁旧楼房而设计的。

6 spiny   

adj.多刺的，刺状的；n.多刺的东西

参考例句：

• This is the Asiatic ornamental shrub with spiny branches and pink blossoms.这就是亚洲的一种观赏灌木，具有多刺的枝和粉红色的花。
• Stay away from a spiny cactus.远离多刺仙人掌。

7 moth   

n.蛾，蛀虫

参考例句：

• A moth was fluttering round the lamp.有一只蛾子扑打着翅膀绕着灯飞。
• The sweater is moth-eaten.毛衣让蛀虫咬坏了。

8 moths   

n.蛾( moth的名词复数 )

参考例句：

• The moths have eaten holes in my wool coat. 蛀虫将我的羊毛衫蛀蚀了几个小洞。 来自《简明英汉词典》
• The moths tapped and blurred at the window screen. 飞蛾在窗帘上跳来跳去，弄上了许多污点。 来自《现代英汉综合大词典》

9 gaudy   

adj.华而不实的；俗丽的

参考例句：

• She was tricked out in gaudy dress.她穿得华丽而俗气。
• The gaudy butterfly is sure that the flowers owe thanks to him.浮华的蝴蝶却相信花是应该向它道谢的。

10 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

11 tints   

色彩( tint的名词复数 )； 带白的颜色； （淡色）染发剂； 痕迹

参考例句：

• leaves with red and gold autumn tints 金秋时节略呈红黄色的树叶
• The whole countryside glowed with autumn tints. 乡间处处呈现出灿烂的秋色。

12 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

13 abhorrence   

n.憎恶；可憎恶的事

参考例句：

• This nation has an abhorrence of terrrorism.这个民族憎恶恐怖主义。
• It is an abhorrence to his feeling.这是他深恶痛绝的事。

14 magpie   

n.喜欢收藏物品的人，喜鹊，饶舌者

参考例句：

• Now and then a magpie would call.不时有喜鹊的叫声。
• This young man is really a magpie.这个年轻人真是饶舌。

15 dread   

vt.担忧，忧虑；惧怕，不敢；n.担忧，畏惧

参考例句：

• We all dread to think what will happen if the company closes.我们都不敢去想一旦公司关门我们该怎么办。
• Her heart was relieved of its blankest dread.她极度恐惧的心理消除了。

16 detailed   

adj.详细的，详尽的，极注意细节的，完全的

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。

17 weir   

n.堰堤，拦河坝

参考例句：

• The discharge from the weir opening should be free.从堰开口处的泻水应畅通。
• Big Weir River,restraining tears,has departed!大堰河，含泪地去了！

18 aviary   

n.大鸟笼，鸟舍

参考例句：

• There are many different kinds of birds in the aviary.大鸟笼里有很多不同种类的鸟。
• There was also an aviary full of rare birds.那里面还有装满稀有鸟类的鸟舍。

19 robin   

n.知更鸟，红襟鸟

参考例句：

• The robin is the messenger of spring.知更鸟是报春的使者。
• We knew spring was coming as we had seen a robin.我们看见了一只知更鸟，知道春天要到了。

20 impunity   

n.(惩罚、损失、伤害等的)免除

参考例句：

• You will not escape with impunity.你不可能逃脱惩罚。
• The impunity what compulsory insurance sets does not include escapement.交强险规定的免责范围不包括逃逸。

21 spines   

n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊

参考例句：

• Porcupines use their spines to protect themselves. 豪猪用身上的刺毛来自卫。
• The cactus has spines. 仙人掌有刺。 来自《现代英汉综合大词典》

22 persistently   

ad.坚持地；固执地

参考例句：

• He persistently asserted his right to a share in the heritage. 他始终声称他有分享那笔遗产的权利。
• She persistently asserted her opinions. 她果断地说出了自己的意见。

23 spined   

adj.有背骨的，有刺的，有脊柱的

参考例句：

• Thesolution of collagen-PVA was wet spined with the sodium sulfate as coagulant and collagen-PVA composite fibers were prepared. 在此基础上，以硫酸钠为凝固剂，对胶原-PVA共混溶液进行湿法纺丝，制备了胶原-PVA复合纤维。 来自辞典例句
• In the case of the nine-spined stickleback, they have most likely adapted to local ecology. 对于九刺鱼来说，他们很有可能的是出于适应本身所处的生态环境而习就了这一高级功能。 来自互联网

24 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

25 conceal   

v.隐藏，隐瞒，隐蔽

参考例句：

• He had to conceal his identity to escape the police.为了躲避警方，他只好隐瞒身份。
• He could hardly conceal his joy at his departure.他几乎掩饰不住临行时的喜悦。

26 conspicuously   

ad.明显地，惹人注目地

参考例句：

• France remained a conspicuously uneasy country. 法国依然是个明显不太平的国家。
• She figured conspicuously in the public debate on the issue. 她在该问题的公开辩论中很引人注目。

27 spotted   

adj.有斑点的，斑纹的，弄污了的

参考例句：

• The milkman selected the spotted cows,from among a herd of two hundred.牛奶商从一群200头牛中选出有斑点的牛。
• Sam's shop stocks short spotted socks.山姆的商店屯积了有斑点的短袜。

28 lateral   

adj.侧面的，旁边的

参考例句：

• An airfoil that controls lateral motion.能够控制横向飞行的机翼。
• Mr.Dawson walked into the court from a lateral door.道森先生从一个侧面的门走进法庭。

29 apparently   

adv.显然地；表面上，似乎

参考例句：

• An apparently blind alley leads suddenly into an open space.山穷水尽，豁然开朗。
• He was apparently much surprised at the news.他对那个消息显然感到十分惊异。

30 relished   

v.欣赏( relish的过去式和过去分词 )；从…获得乐趣；渴望

参考例句：

• The chaplain relished the privacy and isolation of his verdant surroundings. 牧师十分欣赏他那苍翠的环境所具有的幽雅恬静，与世隔绝的气氛。 来自辞典例句
• Dalleson relished the first portion of the work before him. 达尔生对眼前这工作的前半部分满有兴趣。 来自辞典例句

31 twigs   

细枝，嫩枝( twig的名词复数 )

参考例句：

• Some birds build nests of twigs. 一些鸟用树枝筑巢。
• Willow twigs are pliable. 柳条很软。

32 lizards   

n.蜥蜴( lizard的名词复数 )

参考例句：

• Nothing lives in Pompeii except crickets and beetles and lizards. 在庞培城里除了蟋蟀、甲壳虫和蜥蜴外，没有别的生物。 来自辞典例句
• Can lizards reproduce their tails? 蜥蜴的尾巴断了以后能再生吗？ 来自辞典例句

33 corroborate   

v.支持，证实，确定

参考例句：

• He looked at me anxiously,as if he hoped I'd corroborate this.他神色不安地看着我，仿佛他希望我证实地的话。
• It appeared that what he said went to corroborate my account.看来他所说的和我叙述的相符。

34 voracious   

adj.狼吞虎咽的，贪婪的

参考例句：

• She's a voracious reader of all kinds of love stories.什么样的爱情故事她都百看不厌。
• Joseph Smith was a voracious book collector.约瑟夫·史密斯是个如饥似渴的藏书家。

35 devouring   

吞没( devour的现在分词 )； 耗尽； 津津有味地看； 狼吞虎咽地吃光

参考例句：

• The hungry boy was devouring his dinner. 那饥饿的孩子狼吞虎咽地吃饭。
• He is devouring novel after novel. 他一味贪看小说。

36 devour   

v.吞没；贪婪地注视或谛听，贪读；使着迷

参考例句：

• Larger fish devour the smaller ones.大鱼吃小鱼。
• Beauty is but a flower which wrinkle will devour.美只不过是一朵，终会被皱纹所吞噬。

37 humble   

adj.谦卑的，恭顺的；地位低下的；v.降低，贬低

参考例句：

• In my humble opinion,he will win the election.依我拙见，他将在选举中获胜。
• Defeat and failure make people humble.挫折与失败会使人谦卑。

38 gaping   

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

参考例句：

• Ahead of them was a gaping abyss. 他们前面是一个巨大的深渊。
• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。 来自《简明英汉词典》

39 morsels   

n.一口( morsel的名词复数 )；（尤指食物）小块，碎屑

参考例句：

• They are the most delicate morsels. 这些确是最好吃的部分。 来自辞典例句
• Foxes will scratch up grass to find tasty bug and beetle morsels. 狐狸会挖草地，寻找美味的虫子和甲壳虫。 来自互联网

40 jaws   

n.口部；嘴

参考例句：

• The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
• The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。

41 funnel   

n.漏斗；烟囱；v.汇集

参考例句：

• He poured the petrol into the car through a funnel.他用一个漏斗把汽油灌入汽车。
• I like the ship with a yellow funnel.我喜欢那条有黄烟囱的船。

42 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

43 confirmation   

n.证实，确认，批准

参考例句：

• We are waiting for confirmation of the news.我们正在等待证实那个消息。
• We need confirmation in writing before we can send your order out.给你们发送订购的货物之前，我们需要书面确认。