8 SOUTH-AFEICAN BUTTEEFLIES. 



tion of cocoon which they carry about with them, and from which only 

 the head and front segments bearing the legs protrude. These silken 

 fabrics are externally both strengthened and disguised by attached 

 pieces of objects among which the larva lives, such as woollen tissue 

 (in the case of the Olothes-Moth caterpillars), sand, small particles 

 of stone, bits of grass, or sticks. In the case of many of the latter, 

 the bits of grass or sticks are most neatly cut of the required length, 

 and firmly secured in most regular order, the whole resembling the 

 conventional fasces of the Roman lictor. 



Caterpillars are, apparently, of all insect larvee the most liable 

 to attack by the parasitic Hymenoptera, known as Ichneumon-flies 

 {families Ichncumonidce, Chalcididce, &c.). The female fly is provided 

 with an acute ovipositor, by means of which she pierces the caterpillar's 

 integument, and introduces her eggs. The grubs of the Ichneumon-fly 

 soon hatch in the caterpillar's body, and begin to devour its tissues. 

 They appear to avoid injuring the vital organs, and to derive nearly all, 

 if not the whole, of their sustenance from the spacious fat-body (corpus 

 adiposum) which envelops the caterpillar's alimentary canal, &c., and 

 fills almost all the space between those organs and the body-walls. The 

 caterpillar so infested usually lives to attain its full size, and sometimes 

 to assume the chrysalis form, but it never reaches the perfect state, its 

 devourers either emerging to spin their own little cocoons around its 

 skin, or undergoing their metamorphosis within it. Other deadly 

 parasites are the species of Tachina, flies of the Order Diptera, which 

 fasten their eggs on the surface of the caterpillar, into whose body the 

 maggots hatched from them penetrate. 



There is much diSerence among caterpillars as regards activity 

 of motion. Those of Butterflies are for the most part remarkably 

 sluggish, scarcely moving except from one leaf to another, and those of 

 the Hawkmoths and higher Bombyces are as a rule but little more 

 active. Among the latter, however, the well-known hairy larv£e of the 

 lovely Tiger-Moths (^Arctvidce) are an exception, being frequent and 

 rapid walkers. The catei-pillars of many of the lower groups of moths 

 (Noctum, Pyralcs, Geomctrce, and Tortrices) are very quick in their 

 motions, a few even exhibiting the power of leaping away when dis- 

 turbed. The Geomctrm larv^ almost invariably have only two pairs of 

 " claspers " or pro-legs, situated posteriorly on tlie tenth and thirteenth 

 segments, with which peculiarity is associated the mode of progression 

 which led to their name ; this consisting of their stretching out the 

 body forward and grasping with the true legs near the head, and then 

 bringing up the pro-legs close to the others, so that the long inter- 

 mediate legless portion of the body is looped or arched. In this way 

 they proceed by long-measured steps, instead of by the continuous 

 undulatory motion of caterpillars with the full complement of pro-legs. 

 These Geometer larvee have in a great many instances the extraordinary 

 power of keeping the body for hours rigidly extended from its base of 



