20 Outline of Life-history 



advantage, as lie says, ' of being descriptive of a cliaracter 

 taken from their metamorphoses on one side, and of 

 another character taken from the imago and its principal 

 organ of orientation (the antennae) on the other. The 

 names OrthorrhapJia and Cyclorrhaplia were very happily 

 chosen by Braner to characterize the metamorphoses of 

 each of these groups, and should therefore be preserved. 

 The names Nemocera and Atliericera were adopted for 

 two groups by Latreille, and should likewise be re- 

 tained ^.' 



Chironomus belongs to the sub-order Orthorrhapha 



Nemocera, in which the only pupal envelope is a thin 



membrane, the proper pupal skin. The antennae are 



slender and many -jointed. 



simpiifica- If a number of different Dipterous larvae are examined, 



larval com- a scries cau be traced which exhibits a twofold gradation, 



phcation of g£pg^j.- j-^g ^i^p 1^^,^,^^ ^^^^ ^1-^e imago in opposite directions, 



the larva becoming simplified as the imago becomes com- 

 plicated. This apparently results from the gradual trans- 

 ference of certain functions and responsibilities from the 

 larva to the imago. In the more primitive forms the 

 larva is active, and moves about to seek its food. Its 

 structure is relatively complex, and its intelligence rela- 

 tively high. The winged insect is short-lived, and the 

 eggs are laid all together. The development of the fly 

 within the body of the larva is gradual, and compatible 

 with active life. Though the pupa does not feed, it never 

 becomes motionless, and the pupal stage is brief. In pro- 

 portion as the fly becomes more expert in seeking out 

 stores of highly nutritious and easily assimilated food for 

 its offspring, the larva degenerates. Some flies lay their 

 ecTcrs in green leaves, in living fungi, or in decaying 

 carcases, and to find out a site which is exactly suitable 

 they often require a comparatively long life, keen senses, 



' Entomol. M. Mag., 1893, pp. 149-150. 



