ANNULOSA : INSECTA. 



275 



do not correspond with those of the adult, though these 

 latter are usually present as well (fig. 107). 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," 

 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 



Fig. 107. Metamorphosis of the Magpie- 

 moth (Phalcena grossulariata) . 



constitutes what in the case of the Lepidoptera is gene- 

 rally known as the "chrysalis," or "aurelia" (fig. 114). The 

 body of the pupa is usually covered by a chitinous pellicle, 

 which closely invests the animal. In some cases (e.g., in many 

 Dipterous insects) no traces can be detected in the pupa of the 

 future insect ; but in the Lepidoptera the thorax and abdomen 

 are distinctly recognisable in the pupae; whilst in others (<?.-., 

 Hymenopterd] the parts of the pupa are merely covered by a 

 membrane and are quite distinct. In some cases the pupa is 

 further protected within the dried skin of the larva ; and in 

 other cases the larva immediately before entering upon the 

 pupa-stage spins, by means of special organs for the purpose, 

 a protective case, which surrounds the chrysalis, 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, consists of male and 



