134 ESSAY ON CLASSIFICATION. 



at an age which forms a much longer part of the whole 

 duration of life. In Insects the period of maturity is, on 

 the contrary, generally the shortest, while the growth of 

 the larva is very slow, or, at least, that stage of de- 

 velopment lasts for a much longer time than the life of 

 the perfect Insects. There is no more striking example 

 of tins peculiar mode of growth than the seventeen years 

 locust, so fully traced by Miss M. H. Morris. 1 



Whilst all long-lived animals continue, as a matter of 

 course, their existence through a series of years, under the 

 varying influence of successive seasons, there are many 

 others which are periodical in their appearance ; this is 

 the case with most insects, 2 but perhaps in a still more 

 striking manner with Medusas. 3 



The most interesting point, however, in this subject is 

 the change of character wilich takes place in the different 

 stages of growth of one and the same animal. Neither 

 Vertebrates nor Mollusks, nor even Eadiates, exhibit in 

 this respect anything so remarkable in the continuous 

 changes which an individual animal undergoes as Insects, 

 and among them those with so-called complete meta- 

 morphosis. Here the young (the larva) is an active, 

 wormlike, voracious, even carnivorous being, which in 

 middle age (as a chrysalis) becomes a mummy-like, almost 

 motionless maggot, incapable of taking food, and ends 

 life as a winged and active insect. Some of these larvse 

 are aquatic and very voracious, when the perfect insect 

 is aerial and takes no food at all. 4 



1 See also HARRIS'S Insects in- 4 BURMEISTER'S Handb. d. Entom. 

 jurious to Vegetation, p. 184, 2d. etc. LACORDAIRE, Introd. a I'Euto- 

 edit. p. 180. mologie, etc. KIRBY and SPENCE, 



2 HEROLD, (E.,)Teutscher Raupen- Introd. to Entomol., etc., q. a., give 

 Kalender, Nordhausen, 1845. accounts of the habits of Insects 



3 AGASSIZ'S Acalephs of North during their metamorphoses. 

 America, p. 228. 



