19 1 O.J N. Annandale : Species of Phlebotomus. 41 



from it at a distinct angle. In Phlebotomus this cross-vein is of 

 extreme delicacy and, unlike the other veins, it is not provided 

 with a double line of hairs. It can onl}' be seen after prolonged 

 staining of the wing, and even then is faint and indistinct. The 

 next transverse vein that is apparent joins the base of the second 

 longitudinal to the first and is marked x in the diagrams ; it is 

 further from the base of the wing in Cidcx than it is in Phlebotomus. 

 Strictly speaking this is not a distinct vein but an upturned 

 portion of the lower vein. The base of the third longitudinal in 

 both genera ends in a small fork, one branch joining the vein to 

 the second longitudinal, the other to the fourth. The former 

 branch is called by Theobald the supernumerary cross-vein, the 

 latter the mid cross-vein. In Phlebotomus, however, the lower 

 branch appears to be in actual continuity wi h the vein, while 

 the upper one joins it at an angle. This is more distinct in some 

 species than in others. In Culcx the fourth and sixth longitudi- 

 nals do not appear to be joined together at the base; but in 

 Phlebotomus the fifth arises from the base of the sixth, as can be 

 seen distinctly in some species, while it is connected with the 

 fourth b}^ a short cross- vein close to its base. 



The venation of Phlebotomus, taking into consideration the 

 above facts, may therefore be said to resemble that of Culex in 

 some essential points, but to differ from it mainly in the fact that 

 the cross-veins are extremeh^ delicate and are situated exclusively 

 on the proximal part of the wing. 



From a systematic point of view, as regards specific differen- 

 tiation, the most important feature in the venation is the relative 

 proportions between the length of the upper branch of the second 

 longitudinal, the distance between the two forks of this vein, and 

 that between the proximal fork and the point at which the vein is 

 joined by the mid cross-vein to the third longitudinal. 



In Phlebotomus. but not in some of its allies {e.g., Diplonenia), 

 the wing is almost devoid of scales, a few of which occur at the 

 extreme base on the costal and lower borders and on those veins 

 which reach the base. Each vein except the small cro^s-vein that 

 joins the subcostal to the costal, b^ars a double row of fine hairs, 

 and the edge of the wing is deeply fringed with longer hairs. 



External genitalia — 



The visible female genitalia in Phlebotomus are simple in 

 structure, consisting of two pairs (a superior and an inferior pair) of 

 compressed, more or less leaf-like appendages covered with sensory 

 hairs. They offer in their shape and proportions features of diag- 

 nostic importance but become shrivelled and distorted in dried 

 specimens. There is no horny ovipositor such as is found in 

 Psychoda and Pericoma. 



The male genitalia are far more complicated anil of much 

 greater systematic importance. It is possible, moreover, to trace 

 their specific differences even in specimens which have been dried, 

 but even such specimens should l)e mounted in canada balsam for 



