BITING MIDGES — WIRTH AND BLANTON 257 



employ an exact measurement of the wing length, comprising the 

 distance from the basal arculus to the tip of the wing, which is about 

 a tenth less than the measurement to the basal attachment of the 

 wing commonly employed by other authors. The color of the 

 halter is frequently of taxonomic importance. 



Abdomen: The female abdomen is relatively stout, the apex 

 somewhat tapered, with a pair of small, rounded cerci visible below 

 the ninth tergum. Internally the female usually possesses sclerotized 

 spermathecae which are usually spherical to pyriform, sometimes 

 with the bases of the ducts sclerotized a short distance. The number 

 of completely formed, sclerotized spermathecae varies from none 

 to three; all the known Panama species have one or two. The 

 spermathecae are joined by nonsclerotized ducts to a common duct, 

 and at the juncture there is sometimes a small sclerotized ring. In 

 some species with two functional spermathecae the small rudimentary 

 third one is also sclerotized. In our descriptions we make no mention 

 of this third rudimentary spermathecae and ring. We measure the 

 length of the spermatheca in the axis of the base of the duct and 

 include the sclerotized portion of the duct. 



The male abdomen is very slender and bears terminally the prom- 

 inent genitalia, which are of primary importance in group classification 

 and species identification. The ninth segment is in the form of an 

 irregular sclerotized ring consisting of the fused tergum and sternum. 

 The ninth tergum is in the form of an expanded lobe or plate, convex 

 externally and hollowed out mesad and bearing the anus flanked by 

 a pair of membranous setose anal lobes or cerci on the ventromesal 

 face. The hind corners of the ninth tergum are frequently expanded 

 as a pair of apicolateral processes. The ninth sternum is much shorter 

 than the tergum, usually with a caudomedian excavation on its hind 

 margin, at the lateral corners of which the base of the aedeagus 

 articulates. The forceps-like genital appendages, or gonopods, arise 

 laterally at the base of the tergum and are 2-segmentcd. The enlarged 

 basal segment (basistyle or side piece) bears two internal processes 

 at the base, a mesally directed ventral root and an anteriorly directed 

 dorsal root, the latter articulating directly with the base of the 

 paramere. The distal segment (dististyle or clasper) is hairy and 

 slightly swollen at the base, slender and nearly bare distally, with 

 an incurved point, and when not extended is folded mesad from the 

 apex of the basistyle across the mesal face of the ninth tergum. The 

 aedeagus is usually a Y-shaped structure with the stem directed 

 ventrocaudad, forming the sclerotized support on the ventral surface 

 of the male genital duct. The distal portion of the aedeagus is less 

 sclerotized than the basal arms or arch, is usually shallowly U-shaped 

 in cross section and may be variously ornamented or modified distally 



