224 THE POPULAR SCIENCE MONTHLY. 



ing place. The female takes care to place her eggs in conditions 

 which will permit her progeny to find food for themselves from 

 birth; but her solicitude usually ends at this point, while she 

 leaves it to the rays of the sun to do the rest a happy arrange- 

 ment, for in most cases the parents die before the hatching. The 

 embryo is developed rapidly under the influence of the ambient 

 heat, and in a short time breaks the shell or springs the cover. 



From the egg issues a being very little or not at all like 

 its parents. Insects, indeed, undergo, before attaining full de- 

 velopment, a series of transformations which are designated as 

 metamorphoses. These metamorphoses are complete or incom- 

 plete ; and there are even what we might call hypermetamorpho- 

 ses, as in the case of the cantharides, the evolutional life of which, 

 only recently well understood, is much more complicated than 

 that of most other insects. The metamorphosis is said to be in- 

 complete when the forms of the young insects, on coming out 

 from the egg, are like those of the adult. Insects whose meta- 

 morphoses are complete come from the egg in the form of larvae. 



The growth of the insect all takes place during the larval 

 state, and is very rapid. The superficial envelope soon becomes 

 too small for the body it contains. So, at determinate periods of 

 their existence, larvae change their skin, or, to speak more accu- 

 rately, burst the integument which envelops them, and shed it. 

 This transformation constitutes the molting, which is repeated 

 from three to eight times, according to the species. During these 

 periods of transition, the larva, as if ill, loses its insatiable appe- 

 tite, ceases to eat, and becomes stationary. 



Insects of incomplete metamorphosis likewise acquire their 

 full development through successive moltings. Each of the 

 moltings is attended by a corresponding perfectionment of some 

 part of the organism. 



Larvae of insects often have a horned head, with jaws that 

 permit them to crush food. This conformation also occurs in the 

 larvae of insects which in the adult state have the mouth organ- 

 ized for suction. Some larvae of Dipterce,, however, have the fore 

 part of the body terminated by a pointed and retractile append- 

 age ; they might be spoken of as acephalous. 



After the head come the rings, very like one another, and not 

 exceeding a dozen in number. In these there are three varieties 

 of structure : larvae having only articulated legs (Fig. 2, upper) ; 

 those having both articulated and membranous legs ; and apod- 

 ous larvae, or those having no legs (Fig. 2, lower). 



In the first variety the articulated legs, which end in one or 

 two claws, are attached to the three rings immediately following 

 the head, each ring supporting a pair of legs. The same rings 

 form, at a later stage, the thoracic casing of the perfect insect. 



