286 INSECT ARCHITECTUEE. 



paring one of these with a similar cocoon of the large egger- 

 moth (^Lasiocampa Quercus^, we find no air-holes in the 

 latter, as we might have been led to expect from the close- 

 ness of its texture. We found a cocoon of a saw-fly {Trichi- 

 osoma), about the same size as that of the egger, attached to 

 a hawthorn twig, in a hedge at New-Cross, Deptford, but 

 of a leathery texture, and, externally, exactly the colour of 

 the bark of the tree. During the summer of 1830 we 

 found a considerable number of the same cocoons. These 

 were all without air-holes. The egger, we may remark, 

 unlike the dock-weevil or the bee-grub just mentioned, can 

 work her cocoon without any point of attachment. We 

 had a colony of these caterpillars in the summer of 1825, 

 brought from Epping Forest, and saw several of them work 

 their cocoons, and we could not but admire the dexterity 

 with which they avoided filling up the little pin-holes. 

 The supply of their building material was evidently mea- 

 sured out to them in the exact quantity required ; for when 

 we broke down a portion of their wall, by way of experi- 

 ment, they did not make it above half the thickness of the 

 previous portion, though they plainly preferred having a 

 thin wall to leaving the breach unclosed. (J. E.) 



Several species of caterpillars, that spin only silk, are 

 social, like some of those we formerly mentioned, which 

 unite to form a common tent of leaves (see pages 151, 152). 

 The most common instance of this is in the caterpillars 

 which feed on the nettle — the small tortoise-shell ( Vanessa 

 urticcB), and the peacock's eye ( V. I.) Colonies of these 

 may be seen, after Midsummer, on almost every clump of 

 nettles, inhabiting a thin web of an irregular oval shape, 

 from which they issue out to feed on the leaves, always re- 

 turning when their appetite is satisfied, to assist their com- 

 panions in extending their premises. Other examples, still 

 more conspicuous from being seen on fruit-trees and in 

 hedges, occur in the caterpillars of the small ermine-moth 

 ( Yponomeuta padella), and of the lackey {Clisiocampa neustria), 

 which in some years are but too abundant, though in others 

 they are seldom met with. In the summer of 1826, every 

 hedge and fruit-tree around London swarmed with colonies 



