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THE METAMORPHOSES OP INSECTS. 



Nothing' ill tlie liistoiy of insects is more remarkable tliau the striking 

 clianges of form wliicli many of them undergo, in tlie course of their 

 development. Whilst other animals progress from infancy to maturity 

 simply by a process of growth, nnd by such gradual and imperceptible 

 changes only as their growth necessitates, many insects assume totally 

 different forms in the conrse of their development, so that they conld 

 never be recognized as the same individuals, if this development had 

 not been actually traced from one stage to another. These changes are 

 called the metamorphoses or transformations of insects. All insects, in 

 their growth, pass through four stages, designated as the egg state ; the 

 ?arm, or caterpillar state ; the j;?y9rf, or chrysalis state; and the imago, 

 or i)erfect and winged state. The metamorphoses of insects are of two 

 principal kinds, complete and incomplete. 



In the complete metamorphosis the larva bears no resemblance to the 

 imago, and the insect, in the intermediate or pupa state, is motionless, 

 and takes no food. This kind of metamorphosis presents two principal 

 varieties. In some (Lepidoptera and many Diptera), the legs and wings 

 are comi)letely hiclosed in the pupa case. In others (Coleoptera, Hy- 

 menoptera, and some others), the legs of the pupa, though useless, are 

 free, and the rudimental wings lie loosely npon the sides. Moreover, in 

 some (the nocturnal Lepidoptera, and many Hymenoptera), the pupa 

 is inclosed in a separate covering or cocoon, whereas the majority 

 of insects have no such covering. Pni^ie thus inclosed are called foUi- 

 culate. The term chrysalis, from a Greek word meaning golden, is some- 

 times applied to the puppe of the dinrnal Lepidoptera, because the 

 pupte of some butterflies are ornamented with golden spots. 



Most insects, in changing from the larva to the pupa state, cast off the 

 larval skin, but in many of the tw^o-Avinged flies, (Muscid.T, Syri^hida?, 

 etc.) the larval skin becomes contracted and hardened, assumes an oval 

 form and a brown color, and thus forms a compact and closely-fitting 

 case, in which the pnpa proper is inclosed, but distinct. Pnppe thus in- 

 closed are called coarctate, and their cases are analogous to the cocoons 

 of the Lepidoptera. 



In the incomplete metamorphosis, the insect presents essentially the 

 same form, and is active in all its stages, after lea\aug the ^gg. The 

 pupa is distinguished from the larva by the presence of short rudimen- 

 tal wings at the base of the abdomen, and the imago or adult state is 

 distinguished by the fully grown wings and wing-covers. It is only in 

 this last stage that insects are capable of propagation. All the Hemip- 

 tera, or bngs proper, and all the Orthoptera, or crickets, grasshoppers 

 and cockroaches, exhibit this imperfect kind of metamoiphosis. 



