226 DIRECT BENEFITS DERIVED FROM iNSECTS. 



very beautiful silk, of dazzling whiteness, may be collected from the 

 cocoons even of the Ichneumons that destroy the larvae of some moth in 

 the West Indies, which feed upon the indigo and cassada.^ 



It is probable, too, that other articles besides silk might be obtained 

 from the larvae which usually produce it, particularly cements and varnishes 

 of- different kinds, some hard, others elastic, from their gum and silk 

 reservoirs, from which it is said the Chinese procure a fine varnish, and 

 fabricate what is called by anglers Indian grass.^ The diminutive 

 size of the animal will be thought no objection, when we recollect that 

 the very small quantity of purple dye afforded by the Purpura of the 

 ancients did not prevent them from collecting it. 



I now conclude this long series of letters on the injuries caused by 

 insects to man, and the benefits which he derives from them ; and I think 

 you will readily admit that I have sufficiently made good my position 

 that the study of agents which perform such important functions in the 

 economy of nature must be worthy of attention. Our subsequent cor- 

 respondence will be devoted to the most interesting traits in their history 

 — as their affection to their young, their food and modes of procuring it, 

 habitations, societies, &c. 



I am, &;c. 



higher walks of philosophy from insects, that astronomers employ the strongest thread of 

 spiders, the one namely that supports the web, for the divisions of the micrometer. By its 

 ductility this thread acquires about a fifth of its ordinary length. Nouv. Diet, d' Hist. Nat. 

 ii. 280. 



' American Fhil. Tram. v. 325. 



* Andersoa's Recreations in Agriculture, &c. iv. 399. 



