IXTRODUCTIO.V. XV 



on the segments ; other larvje liave rows of transverse spots between the first segments, or are 

 covered with large or small spots, var\'ing in number, and often arranged in rows or in transverse 

 bands (compare the larvse figured on PI. 39). 



Moulting. — As the outer skin of the larva does not expand with its growth, it is cast off when 

 it becomes too narrow. This phenomenon is called moulting. It takes place at more or less 

 regular intervals, usually after from six days to a fortnight, but sometimes at much longer 

 intervals, especially in cases when hybernation intervenes. Some larvse moult twice only, others 

 seven times, but the greater number four or five times. During the time of moulting the larva 

 appears to be ill. It ceases to eat, and fixes itself firmly with the prolegs and claspers. The old 

 skin becomes dry and shrivelled ; a new and larger head appears behind the old head ; and at last 

 the old skin splits down the back behind the head, and the lar\'a, clothed in a new skin, extricates 

 itself gradually from the old one. The empty shell of the old head generally remains sticking to 

 the mouth of the new head for a little while, till it is rubbed off. In hairy and spiny larvae the 

 hairs and spines are thrown off with the old skin, under which the new hairs and spines lie close to 

 the body in a limp condition, and stiffen and become dry after the old skin is thrown off. All the 

 other parts slip out of the old skin, in which they are enclosed. Even the lining of the intestines 

 and breathing tubes is thrown off with the old skin, according to some writers. The colour and 

 pattern of the larva, and in some cases even its shape, are liable to considerable alteration after 

 moulting. Thus the larva; of Aglia Tmi lose the small spines wliich they possess on first quitting 

 the egg ; and the larvse of many Noctiice, which have the first pair of prolegs imperfect in their 

 earlier stages, and consequently walk somewhat like loopers, acquire perfectly developed prolegs 

 after the two first moults. 



Habits. — The food of larvse consists almost exclusively of vegetable substances, though the 

 larvse of some Micro-Lcpidoptcra form an exception, as they live upon animal substances, such as 

 hair, feathers, wool, &c., or on animal products, such as grease, the wax in the nests of bees and 

 humble-bees, &c. The larvje of some Nocticce and Geomctrce, for instance, those of the genus 

 Cosmia, and of Scopdosoma Satcllitia and Crocallis Elinguaria, will devour other larv^ which 

 may happen to be in their company. It is even doubtful whether the larva of Senta Maritima 

 does not feed exclusively on other insects. Most of the larvse which feed on plants li\'e on the 

 softer portions, such as the leaves and flowers ; but there are many which feed on other parts : some 

 on the buds, fruits, or seeds, and others live in the interior of the stem, or in the bark, wood, and 

 roots, often burrowing in the solid wood. Thus the larvse of the Sesiidce live and feed in or under 

 the bark and in the wood of trees, or in the roots of herbaceous plants ; the larvEe of the genera 

 CossHs and Zcii:;cra also live in the trunks of trees; those of P/irag//iata'cia, Hjdracia, Gortyna, 

 Helotropha, Nonagria, and Calainia feed in the stems of plants, and sometimes creep down into the 

 roots, while those of the genus Dianthcccia live in the seed-capsules of plants allied to the pink. 

 The larvae of the genus Agrotis, &c., live on or just beneath the surface of the ground, and 

 frequently do great injury by eating through the roots of cultivated plants — a habit which has led 

 to their being called " cut-worms" in America. Several other larvse besides those which we have 

 mentioned above feed in the interior of plants. These chiefly belong to the Micro- L cpidoptera ; 

 and a great number of them burrow in the leaves of plants, and are called mining larvae. 

 These live between the upper and under cuticle of leaves, and feed upon the green substance called 

 chlorophyl, thus forming colourless spots or galleries in the leaf Su:h mines are formed by most 

 larvse belonging to the families Elachistidce, Lithocollctida;, Lyoiictidcc, Xeptiailid(V,3.\\d Colcop/wridce. 

 The last have the additional peculiarity of living in cases, from which they stretch out their heads 

 to eat into the leaf, while the hinder part of their body remains in the case, and thus they hold 



