172 HABITS AND INSTINCTS OP ANIMALS. CHAP. V. 



whether this gummy covering assists them to capture 

 their prey, or acts as a defence against their enemies, we 

 were unable to ascertain. Many beetles are defended 

 by prickly spines, either upon the wing-cases or the legs ; 

 and others, from the extreme hardness of their exter- 

 nal covering, will set the pin of the entomologist at de- 

 fiance. Even the skin of the common horse-fly {Hip- 

 pobosca equina Lin.) is so tough, that the utmost pressure 

 of the ringer and thumb will scarcely deprive the insect 

 of life. Numerous insects are provided with involun- 

 tary secretions, for the defence of their young, or of 

 themselves. Among the former, none is more familiar 

 than the little drops of white froth so frequently seen 

 an the plants and shrubs of our garden during summer, 

 and which is usually called by the vulgar cuckoo-spit. 

 Within each of these will be found a little soft pale 

 green insect, with an enormous head and no wings : 

 this is the larva or caterpillar of the Cicada spumaria, 

 or frog-hopper, generally inhabiting the same plants. 

 Our apple trees are well known to suffer from what is 

 called the American blight, the little bits of white 

 cotton-like substance, which is the outward sign of 

 this disease, being the covering of the insects and their 

 eggs, intended, probably, to protect both from the rain. 

 Mr. Kirby suggests that this secretion is either for con- 

 cealment, or to render them distasteful to creatures 

 that would otherwise prey upon them. 



(189.) Passive defence is also effected by the great 

 vitality of some tribes, whether in surviving injuries 

 which would kill other creatures, or recovering from 

 the effects of severe wounds. It really seems im- 

 possible for us to kill many insects, without injuring 

 them too much for our cabinets, a circumstance which 

 is a source of regret and pain to every feeling mind. 

 Grasshoppers will sometimes outlive immersion in 

 boiling water ; and, unfortunately, survive the removal 

 of their intestines. A mite has been known to live 

 eleven weeks, without food, gummed to the point of a 

 pin : and Swammerdam affirms, that the chamaeleon fly 



