240 



MANUAL OF ZOOLOGY. 



which differ greatly from one another in appearance, the me- 

 tamorphosis, therefore, being said to be "complete." In these 



insects (fig. 83) the " larva " 

 is vermiform, segmented, and 

 usually provided with loco- 

 motive feet, which do not 

 correspond with those of the 

 adult, though these latter are 

 usually present as well (figs. 

 83, 89). In some cases the 

 larva is destitute of legs, or 

 is " apodal." The larva is 

 also provided with mastica- 

 tory organs, and usually eats 

 voraciously. In this stage of 

 the metamorphosis the larvae 

 constitute what are usually 

 called " caterpillars " and 

 "grubs." Having remained 

 in this condition for a longer 

 or shorter length of time, and 

 having undergone repeated 

 changes of skin, or " moults," 



Fig. 83. Metamorphosis of the Magpie- necessitated by its rapid 



growth, the larva passes into 



the second stage, and becomes a " pupa." The insect is now 

 perfectly quiescent, unless touched or otherwise irritated, is 

 incapable of changing its place, and is often attached to some 

 foreign object. This constitutes what in the case of the 

 Lepidoptera is generally known as the " chrysalis," or " aure- 

 lia" (fig. 88). The body of the pupa is usually covered by a 

 chitinous pellicle, which closely invests the animal. In some 

 cases the pupa is further protected within the dried skin of the 

 larva; and in other cases the larva immediately before en- 

 tering upon the pupa-stage spins, by means of special organs 

 for the purpose, a protective case, which surrounds the chry- 

 salis, and is termed the " cocoon." 



Having remained for a variable time in the quiescent pupa- 

 stage, and having undergone the necessary development, the 

 insect now frees itself from the envelope which obscured it, 

 and appears as the perfect adult, or " imago," characterised by 

 the possession of wings. 



SEXES OF INSECTS. The great majority of Insects, as is the 

 case with most of the higher animals, consist of male and 

 female individuals; but there occur some striking exceptions 



