392 CLASS vin. 



moreover, there may be distinguished in it two short conical an- 

 tennae, two strong mandibles, two maxillse with small palps, and an 

 under-lip, which also has two small palps and terminates in a point, 

 under which the efferent canal of the matter with which the cater- 

 pillar prepares its web is situated. This substance is secreted as a 

 fluid by two long, blind, convoluted vessels, which lie at the sides 

 of the intestinal canal. Most caterpillars live on vegetable food, 

 especially leaves, and many are limited to a single species of vege- 

 table. Others, however, eat leather, fur, fat, wax, &c., and these 

 belong especially to the family of the moths. Caterpillars usually 

 change the skin four or five times before turning into pupae. 



The pupae of scaly-winged insects are quiescent, and move their 

 abdomen alone when they are touched. They are oblong-ovate, and 

 covered with a horny skin (jpupce, obtec'ce, see above, p. 273). The 

 pupse of day-butterflies are usually not inclosed in a web, but merely 

 attached by some threads at their posterior extremity, and hang 

 freely with the head downward, or are fixed transversely to a branch, 

 or other object, by a transverse band, as if in a hoop. The pupae 

 of nocturnal butterflies either lie underground in a cavity that is 

 smooth and even within, and lined with web, or they are inclosed 

 in a cocoon (folliculus), which is fastened to a branch, or to a wall. 

 The web is frequently silken, sometimes very closely woven, some- 

 times loosely ; sometimes it consists in part of finely gnawed fibres 

 of wood interwoven with the threads of web, or of other foreign 

 objects intermixed with the web, crumbs of earth, morsels of leaves, 

 &c. These pupae have commonly a brown or black colour. 



From the pupa of many species, especially of day-butterflies, the 

 perfect insect proceeds after the lapse of a few days. Of such 

 'species there are ordinarily two generations in a year. Of other 

 species, however, the caterpillar or the pupa remains through the 

 winter, and then the perfect insect usually appears only once in the 

 yeai*, in spring or in summer. Eggs that are laid in autumn are 

 mostly hatched in the following spring. 



The intestinal canal of caterpillars is straight, and consists in 

 great measure of a wide cylindrical stomach. There are four very 

 long vessels for secretion of urine. The perfect insect has a narrow 

 oesophagus with a lateral expansion or crop (the so-called sucking 

 bladder, see above, p. 310) ; the stomach has become shorter, the 

 rest of the intestinal canal longer. Lepidopterous insects in the 

 perfect state of butterflies either take no food at all, or suck the 



