Brauer's Classification 23 



Larval head minute, lialf-retractile ; the month-parts, 

 antennae, and eye-spots much reduced. Pupa inactive, 

 enclosed within the larval skin ; commonly lasts through 

 the winter (five to seven days in summer). Eggs laid 

 all together on water- weeds. 



4. GalUphora (Blow-fly).— Larva very sluggish, im- 

 mersed in putrid flesh. Head minute, rudimentar}-, 

 completely retractile, without antennae or eye- spots, and 

 with only a pair of hooks in place of mouth-parts. 

 Eesting-stage complete, passed within the hardened 

 larval skin ; the pupa lasts fourteen to thirty days 

 according to the season, during which time the body is 

 completely reformed. Fly active and long-lived, laying- 

 eggs in several batches, and feeding on nutritious fluids. 



Brauer (1880) has attempted to make use of such Bmuer's 

 differences as these for the purpose of classification, and classifica- 



tion. 



has published a system in which larval characters, and 

 especially the degree of reduction of the larval head, are 

 employed to denote extensive divisions of Diptera. The 

 attempt has not proved satisfactory. Very few Diptera 

 have been studied anatomically in their early stages, and 

 Brauer has sometimes from defective information placed 

 the genera wrongly in his own system (Chironomus and 

 Phalacrocera are examples). Moreover, the organization 

 of the larva is strongly adaptive, and varies with 

 external circ*umstances. Almost every degree of reduc- 

 tion of the larval head can be found in nature, but the 

 amount of reduction may give little information as to 

 the affinities of the insect. Adaptive and finely graded 

 characters prove here, as else^diere, untrustworthy for the 

 definition of large groups. 



The flies of the many species of Chironomus are dis- Adaptive 



. resem- 



tinguished with difficulty, to judge from the characters biancesami 

 employed in systematic books, which are largely drawn in Nemo- 

 from colour, from the relative length of tarsal joints, and '^'^''''' 

 from the arrangement of the setae on the legs. Though 

 the flies are so similar, the larvae and pupae may differ 

 notably according to their species. Some larvae, for 



