268 HALF HOUKS WITH INSECTS. [Packaku. 



selves. This paradox may be explained by a glance at a 

 Selandria larva (Fig. 207) which sometimes occurs on the 

 chestnut. Its body is entirely concealed by a cottony secre- 

 tion which rises half an inch above the body. A group of 

 these sluggish caterpillars could feed exposed on a leaf with 

 impunity. The bark lice, such as Eriosoma, cover them- 

 selves with a cottony exudation which serves as a disguise. 

 Many bright colored flower beetles are protected by their 

 resemblance to the tints of the flowers in which they hide. 

 The Galeruca and Clytus, almost invariably found on the 

 golden rod in September, are thus protected. 



Why butterflies are so much more commonly seen than 

 their caterpillars is not known. It is probabl^^ due to the 

 j,jQ_ 207. ^^^^ ^^^^ ^^^^ latter are often of 



the color of the leaves on which 

 they feed. The caterpillar of the 

 Colias Philodice, our common sul- 

 phur yellow butterfly, which lives 

 on clover, is rarely found, owing 

 to its pea-green tint so much like 

 Selandria Larva. ^ij^t of the clover leaf on which it 



feeds. It is possible that the caterpillar is so well protected 

 that the butterflies can aftbrd to have their numbers thinned 

 out by predaceous insects and birds. So with tlie caterpil- 

 lars of the white cabbage butterflies, whose dark green vel- 

 vety coats so thoroughly assimilate them with cabbage or 

 turnip leaves or stalks. The caterpillar of Vanessa Antiopa 

 is one of the most conspicuous objects in nature, large clus- 

 ters of these black spiny creatures feeding exposed on the 

 leaves of the willow and other plants. It is probable, how- 

 ever, that bristling as they are with spines, birds do not 

 fancy them ; but the butterflies as well as the chrysalides 

 assume the tints of dead leaves and old 'wood, and the but- 

 terfly may be easily confounded with the trunks of the trees 

 on which it rests, as it does not settle on the ground as in 



12 



