THE PUPAL STAGE OF CULEX. 53 



of the female, beneath the halteres. The male, therefore, would 

 appear to be endowed with a special and very largely developed pair 

 of organs for detecting the whereabouts of the female. 



The female imago, after impregnation, has to find a suitable place 

 to lay her eggs, i.e., the surface of a stagnant pool ; and having 

 found it, has to lay the eggs at a suitable season, and this in the 

 case of females escaping from the pupa late in the summer involves 

 the necessity of living through the winter. Hence the mouth 

 appendages are specially adapted for piercing the skin and extracting 

 the blood of mammals, and this is stored in her capacious stomach. 

 The structure of the mouth-parts in the two sexes has been 

 described by Dimmock (5) ; but as he appears uncertain as to the 

 injection of "saliva" into the wound, I shall add that a special 

 apparatus developes during pupal life by which the saliva is dis- 

 charged near the tip of the hypopharynx (" lingua "). 



Having now given a brief outline of the life-history of the 

 gnat, I will proceed to describe the pupa and the changes which it 

 undergoes in more detail. As, however, I have directed my attention 

 almost exclusively to the more important organs of the body, and 

 not to hairs and the like, I shall not make any distinction of species. 

 What I have to record is probably applicable to all species alike. 



DESCRIPTION OF THE PUPA OF CULEX. 



The External Characters. 



The head is broad from side to side ; the epicranium has a well- 

 marked median groove ; the clypeus, broad above, is gradually 

 narrowed below, and continued without any distinct line of demar- 

 cation into the labrum. At the sides are a pair of compound eyes, 

 to be regarded rather as the rudiments of the eyes of the future 

 gnat than as the visual organs of the pupa itself. Their form and 

 size in the earliest stage are shown in Fig. 1. During pupal life they 

 incrca.se in size till they almost encircle the head. Corneal facets 

 are never formed in the pupal cuticle, but beneath it the convex 

 facets of the imaginal cornea are formed during pupal life. 



