246 THE INFANCY OF ANIMALS 



red whips. At the same time, however, they develop a 

 new and more effective weapon of offence, which assumes 

 the diabolical character of vitriol-throwing ! At the 

 lower part of the red margin below the head is a slit-like 

 opening leading into a gland wherein is distilled a highly 

 irritant mixture of formic acid and water, analysis showing 

 the presence of no less than forty per cent, of acid. While 

 this fluid is used on all occasions of alarm, it is more 

 especially employed to ward off the attacks of an ich- 

 neumon fly. 



This insect lays its eggs on the skin of the caterpillar, 

 and these speedily hatch out and bore into the body of 

 their victim, slowly devouring its internal organs, yet 

 avoiding any vital part till their growth is complete. 

 Within the body they then become chrysahdes, and 

 hatching there, emerge in due course as adult ichneumon 

 flies, to start another brood of children trained to murder. 

 To repel such attacks the puss-moth has developed the, 

 under the circumstances, quite legitimate device of " vitriol- 

 throwing," for should the spray of this touch the invading 

 fly, death is the result. 



More singular, however, is the case of the caterpillar of 

 the Lobster-moth, wherein the body has been still further 

 transformed, till it has assumed a shape which, to our eyes 

 at any rate, borders on the grotesque. As will be seen 

 in our illustration, the fore-part of the body bears a series 

 of large spines, while the hinder end is curiously swollen 

 and turned forwards over the back. In this strange 

 position it bears a strong likeness to one of the withered 

 leaves of the beech, on which it feeds. The stalk is formed 

 by a pair of long filaments which are kept close together 

 so as to appear single, while the second and third pairs of 

 legs are extraordinarily long, but the length is halved by 



