CHAPTER X 



THE PROBLEM OF DEFENCE 



In the two preceding chapters we have seen that very 

 man3 r insects derive protection from what is really an 

 elaborate system of fraud. Their identity is hidden, so 

 to speak, behind a mask, and they are thus passed over or 

 avoided by their enemies. But this principle can only be 

 regarded as a first line of defence, which avails just as 

 long as the deception is maintained. For no matter how 

 perfect a resemblance may be, it is always liable to be 

 discovered ; and when this happens, the insect must be 

 able to adopt active measures for defence, or its chance of 

 life is small indeed. 



Certain insects have been observed to assume startling 

 attitudes under the stimulus of alarm, thus scaring away 

 their assailants. A good example is the caterpillar of the 

 lobster moth (Stauropus fagi). Ordinarily, it has the 

 appearance of a withered and crumpled leaf; but when 

 disturbed, it immediately assumes what has been called its 

 " terrifying attitude." In this position it looks like a large 

 spider, but with all the characteristic points of a spider's 

 anatomy greatly exaggerated for the sake of effect. 

 Experiments have shown that this strange defensive habit 

 is of no little avail against the attacks of birds and other 

 insectivorous creatures, which exhibit varying degrees of 

 alarm and disgust at the sudden transformation. More- 

 over, it has been suggested that the spider-like appearance 

 may be especially useful as a safeguard against the attacks 

 of ichneumons. A large and presumably ferocious spider 



ir,2 



