II 



FLIES WITH AQUATIC 



105 



piratory organs at the tail of the larva. Why, then, 

 need this arrangement be reversed when the Insect 

 enters the pupal stage ? There is now no feeding to 

 be done, and it surely does not signify how the head 



FIG. 25. Pupa of Gnat (Culex 

 nemorosus), showing the parts 

 of the fly enclosed in the 

 transparent pupa-skin. The 

 head and thorax are just freed 

 from the pupal skin. 



FIG. 26. Fly of Gnat (Culex nemorosus) 

 escaping from pupa-skin. This and the pre- 

 ceding figure are from specimens mounted 

 in Canada balsam. 



is carried. Why should not the pupa continue to 

 breathe like the larva, by its tail, instead of developing 

 a new apparatus at the opposite end of its body, as 

 if for change's sake ? Well, it does not appear that, 

 so far as the pupa itself is concerned, any good 



