40 Records of ihe hid) an Museum. [\^ol. IV, 



tt;-- Some Diagnostic Characters. 



There is some dispute as to the proper nomenclature of the 

 venation of the wing of the Psychodidse ; but I think it will be 

 sufficient for the purposes of this paper if I compare the wing of 

 Phlehotomus with that of the Culicidse, for not only are the 

 Psychodidse (and especially Phlehotomus) close'y allied to that 

 f amity, but more attention has peihaps been paid to the anatomy 

 of the Culicidse in recent years than to that of any other group 

 of Diptera. I have therefore reproduced the figure of the wing of 

 Culex (fig. i) given by Theobald in the first volume (p. t8) of his 

 Monograph of the CulicidcB side by side with one of the wing of 

 Phlehotonms (fig. 2) on which the same lettering is used. 



In accordance with Theobald's figure and with the views of 

 many diptero'ogists, the thickened anterior or upper border of 

 the wing is called the costa, while the short parallel vein running 

 immediately below it is called the subcosta. The first parallel 

 vein that reaches the distal margin of the wing is known as the 

 first longitudinal, those posterior to it being numbered in numeri- 

 cal succession. In both genera six longitudinal veins can be 

 distinguished. 



The subcosta in Culcx turns upwards at the tip and joins the 

 costa, while in Phlehotomus it turns downwards and joins the first 

 longitudinal. This is a point that will be considered later when the 

 cross-veins are discussed. There is no radical difi'erence as regards 

 the first longitudinal in the two genera except that in the Psy- 

 chodid it turns upwards at the tip and so assumes a superficial 

 resemblance to the subcosta in Culcx, in which it turns downwards. 

 In Culex the second longitudinal forks once, while in Phlehotomus 

 it forks twice. In both genera the third longitudinal is simple 

 and practically straight ; it is much longer in the Psychodid than 

 in Culex. The fourth longitudinal is once forked in both genera, 

 but the fifth is simple in Phlehotomus and bears a branch in Culex ; 

 in both genera the sixth longitudinal is simple and directed down- 

 wards at the distal end. 



The cross-veins are easily detected in Culex, but in Phlehotomus 

 they are very difficult to see owing to their extreme delicacy. In 

 stained preparations, however, their exact position can be detected, 

 at any rate in some specimens. The most noticeable difference 

 as regards them is that while in Culex the more important 

 cross-veins are situated on the distal part of the wing, in Phleho- 

 tomus they are confined entirely to the proximal part. Consider- 

 ing first the anterior half of the wing, we find in Culex a minute 

 cross-vein (the " humeral " cross-vein, not numbered or lettered 

 in the diagrams) joining the subcosta to the costa. In Culex it 

 is situated near the base of the wing, while in Phlehotomus it is 

 practically at the distal end of the very short subcosta, which there- 

 fore appears to be forked. A careful examination shows, however, 

 that the lower branch of the apparent fork is really in continuity 

 with the main stem of the vein, while the cross- vein proceeds 



