II 



FLIES WITH AQUATIC LARVvE 



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 carriecl. 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 



