GROWTH AND METAMORPHOSIS OF INSECTS. 39 



lives, differing greatly in structure, externally and internally, 

 at these three periods, and with a different environment. 



Most caterpillars moult four or five times;* the outer layer 

 of the skin being cast off at each moult. The skin opens 

 on the back behind the head, the caterpillar drawing itself 

 out of the reut. In the change from the caterpillar to the 

 chrysalis, there are remarkable transformations in the mus- 

 cles, the nervous, digestive, and circulatory system, induc- 

 ing a change of form, external and internal, characterizing 

 the different stages in the metamorphosis. 



While the changes in form are comparatively sudden in 

 flies and butterflies, the steps that lead to them are gradual. 

 How gradual they are may be seen by a study of the meta- 

 morphosis of a bee. In the nest of the humble- or honey- 

 bee, the young may be found in all stages, from the egg to 

 the pupa, gayly colored and ready to emerge from its cell. 

 It is difficult to indicate when the chrysalis stage begins 

 and the larva stage ends, yet the metamorphosis is more 

 complete that is, the adult bee is more unlike the larva 

 than in any other insect. 



The better way to understand how an insect transforms 

 is to rear a moth or butterfly, a fly, and a bee or saw-fly 

 from the larva, closely observing each change. By thus 

 observing the transformations of moths, flies, and beetles, 

 the popular opinion that the smaller flies and moths are the 

 young of the larger ones will be seen to be an error; all 

 winged insects being adults, and fully mature. 



* The caterpillars of most North American butterflies moult four 

 times, but in case of hibernation five times, three times being a very 

 rare exception (Psyche, in. 161). Mr. W. Buckler says that the 

 number of moults varies in different species., "I have myself made 

 sure that six is the number for some and nine for others, as in the 

 case'of Nola c-entonalis" (Ent. Month. Mag., July, 1880). Mr. Edwards 

 adds that iu two instances Callosamia promethea moulted but three 

 times, and he thinks that this species varies in the number of moults 

 with the latitude or locality. Telea polypJiemus moults four times, 

 as does Attacus atlas bred in England (Pysche, iii. 171-174). Hellins 

 records a variable number of moults (three to five) in larvse of Orgyia 

 antiqua from the same batch of eggs (Ent. Month. Mag., Sept., 1881, 

 p. 88) 



