122 THE VARIATION OF ANIMALS IN NATURE 



that of the remainder the majority are more easily recognised as 

 adults than as larvae. But this is not always true. Thus Edwards 

 (1929) points out that a number of Chironomid midges are 



Fig. 15. — Respiratory Siphons of Larvve of Culicella morsitans (above) and 

 C. fumipennis, of which the Adults are almost indistinguishable. 



(From Lang, 1920.) 



almost indistinguishable as adults but have totally different 

 larval habits or structure. In some mosquitoes two different 

 types of larvae have been found to produce identical adults 

 (Lang, 1920; Culicella morsitans and C. fumipennis). In this 

 case the larvae are said to be dimorphic, because it is usual 

 to lay most stress on adult structure. The egg-rafts of some 



