COLOURS AND FORMS OF INSECTS. 147 



persuaded, however, that neither a bird, an ichneu- 

 mon, nor a naturalist, would have been apt to fall into 

 such a mistake. 



This family of caterpillars (Geometridce, STEPHENS) 

 have been by collectors not inappropriately named 

 surveyors, loopers, and geometers, from their peculiar 

 manner of moving, which may readily be conceived 

 by those who have not seen them, when we mention 

 that at the commencement of each step their bodies 

 present a pretty exact figure of the Greek letter tt. 

 In this position, laying hold with their hinder prolegs, 

 they stretch out their heads to the full extent of their 

 body, laying hold with their fore legs while they bring 

 forward their body into the 1 form again. 



Such are among the most prominent examples ad- 

 duced by naturalists who advocate the theory that 

 these resemblances to inanimate objects are intended 

 to conceal insects from their enemies.* We shal/ 

 now give a few instances which have suggested 

 themselves as no less corroborative of the opposite 

 doctrine. The first which occurs to us is one of the 

 surveyor caterpillars, whose movements we have just 

 been describing, found very commonly on the cur- 

 rant, the gooseberry, and the black thorn, and called 

 by collectors the magpie (Jlbraxas Grossulariata, 

 LEACH.) This caterpillar is very conspicuous from 

 being spotted, somewhat like the perfect insect, with 

 black upon a bright yellow ground, and contrasting 

 strongly both with the deep green of the leaves upon 

 which it feeds, and the dark-coloured bark upon 

 which it usually rests. The caterpillars of the water 

 betony moth (CucuUia Scrophularice, HUBNER), 

 and of the burnet moth (Euclidia Glyphica, OCH- 

 SEiNHEiM.), are similarly marked with deep black on a 

 yellow ground, which must render them very conspi- 

 cuous. The caterpillars of the small tortoise-shell 



* See Kirby and Spence, Intr, ii, 219-237. 



