BEDROCK 



yellow bodies. Mr. G. F. Leigh, who made the same observation 

 on the corresponding eastern species, at Durban, threw away his 

 first cocoons in the full belief that they were parasitised. 



The characteristic appearance of the abundant " Large Garden 

 White " caterpillar when killed by a minute Braconid parasite must 

 be familiar to many who are not entomologists. The shrivelled 

 body of the victim — commonly found on fences or walls in the 

 autumn — is covered and more or less completely concealed by a 

 mass of little oval yellow cocoons spun by the Bracon larvae imme- 

 diately after their emergence from the caterpillar. The arrangement 

 of the spheres by the African caterpillar is extremely like that of 

 the Bracon cocoons — not only in the loosely heaped mass, but also 

 in the outlying single spheres and groups of two or three. The 

 difference in shape — spherical instead of oval — does not destroy the 

 general impression of strong likeness, although a close examination 

 at once shows that the spheres are composed of a hardened froth. 



What is the advantage of this deceptive appearance of death 

 from the attacks of parasites ? It is not to protect against the 

 parasites themselves ; for the appearance suggests the effect of eggs 

 laid in the body of the caterpillar at a very different and much earlier 

 stage. It is probable that the protection is against insect-eating 

 vertebrate enemies, ready enough to attack a caterpillar or chrysalis 

 of a moth, but not tempted by a heap of tough cocoons each enclosing 

 a small fraction of the nutriment contained in the caterpillar. For 

 this reason probably the yellow or white cocoons of Bracons are 

 such conspicuous objects. 



The instinctive actions by which this deceptive appearance is 

 produced are remarkable and elaborate. Mr. Lamborn has observed 

 that while the silken walls of the cocoon are being built the cater- 

 pillar pauses every now and then and expels a sphere from the 

 posterior extremity of the body. After a little heap has collected, 

 it bends round, encircles a sphere with a few turns of silk, probably 

 to serve as a handle, and then drags it off, arranges it on the growing 

 mass, and fixes it in place with a few more threads. It would be 

 unreasonable to suggest that this elaborate adaptation sprang into 

 being by some ready-made "mutation." The uniformity, size, 

 shape, and colour of the secreted spheres, and their arrangement by 

 means of the appropriate instinctive actions, all contribute to the 



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