INTRODUCTION 



in Kviocephala developed. Usually there is a spinneret beneath 

 the mouth, from which a fine silk is produced. .Segments 2-4 

 bear each a pair of true jointed logs, corresponding to those of 

 the imago, seldom absent. In addition to these there are also 

 in the normal type of Lepidopterous larva ten prologs, suoker- 

 liko extensions, whose extremities are furnished with scries of 

 minute hooks, situated in pairs on segments 7-10 and IS, but 

 some or all of these maybe rudimentary or absent. In the 

 archaic Eriocephala there are prologs on 5-12; and in one or 

 two other instances there are rudimentary paired ventral pro- 

 cesses on other segments than those on which prologs normally 

 appear, but so little developed that it can hardly be deter- 

 mined whether they arc really homologous with the true pro- 

 legs or not. The surface of the body is furnished with 

 numerous dots, spots, or tubercles (variously styled according 

 to their character, which varies much in different species), of 

 which some at least usually boar each a fine hair, or sometimes 

 dense fascicles of hairs ; sometimes theso tubercles are developed 

 into spinous processes, branched with hairs. The spiracles, or 

 orifices of the respiratory tubos, are placed in a row along the 

 sides of the body, not far above the legs. The contractile 

 dorsal vessel, which is the main circulatory organ, runs along 

 the middle of the back, and is often visible through the skin. 



The whole growth of the insect takes place in the larval 

 stage, the increase of bulk being frequently very rapid. 

 During the process the larva casts its skin several times 

 (usually from four to six), sometimes undergoing considerable 

 changes of appearance and habit on those occasions. 



The markings of larvae usually take the form of longitudinal 

 lines; of these the one which runs up the middle of the baok 

 is termed the dorsal, that which includes the spiracles the 

 spiraeular line; those which margin the spiraeular are the 

 supraspiraoular and subspiracular respectively ; between the 

 dorsal and spiraeular are placed two others, the upper being 

 the subdorsal, the lower the lateral. These are seldom all 

 present ; the dorsal and spiraeular alone rest on a structural 

 liasis, the others being assumed by a useful convention. 



Ov 



Hill. 



The ovum, or egg, is small and more or less globular; 

 its surface is frequently sculptured, and assumes special char- 

 acters in particular groups; the colour usually undergoes 

 marked changes during the development of the embryo. 



