BITING MIDGES — WIRTH AND BLANTON 255 



ments 3 to 15 form the flagellum, which in the female is divided into 

 three portions — an elongated third segment, the subequally shortened 

 segments 4 to 10, and the elongated segments 11 to 15. All the 

 flagellar segments bear scattered small hairs, and in addition each of 

 the proximal eight bears a whorl of long hairs, or verticils. In the 

 male, the pedicel is much more enlarged and the transition in the 

 flagellar series occurs between segments 12 and 13, with segments 

 3 to 12 each bearing a whorl of very greatly elongated, erectile verticils 

 forming a more or less dense plume. The presence of one to several 

 minute hyaline sensory discs ringed by dense tufts of very short 

 setae at the apices of certain flagellar segments is a character recently 

 found to be extremely useful in the recognition of species or of species 

 groups. The relative lengths of the segments are also useful in 

 classification, and the antennal ratio, obtained by dividing the com- 

 bined lengths of the last five segments by the combined lengths of the 

 preceding eight, is a convenient way of expressing the most basic 

 relation. 



The mouthparts are well developed, stronger in the female than 

 in the male, and in most species those of the female are especially 

 fitted for piercing and blood-sucking. They are enclosed in an 

 elongated proboscis often as long as the head capsule itself. Inter- 

 nally the sucking apparatus consists of a cibarial and a pharyngeal 

 pump; no characters of the sclerotized parts of the pharyngeal 

 apparatus have yet been found to have taxonomic value such as 

 those described as the "buccopharyngeal apparatus" in other nema- 

 tocerous families. The labium of the female is fleshy, with scattered 

 hairs, enclosing the six other parts, which are slender, distally toothed, 

 sclerotized blades of subequal lengths. These parts consist of a 

 strong, distally toothed labrum, a pair of distally toothed mandibles, 

 a pair of maxillae represented by the bladelike laciniae, and a tubular 

 hypopharynx also bearing distal teeth. The number of teeth on 

 the mandible has been found to be especially useful in differentiation 

 of closely related species. The maxillary palpus is 5-segmented 

 and the third segment is more or less swollen and bears on the mesal 

 surface a specialized sense organ, the nature of which is a very valuable 

 specific character. The mouthparts of the male are similar to those 

 of the female, but much more poorly developed, without distal teeth, 

 and not fitted for piercing. 



Thorax: The thorax is moderately broad and very convex above, 

 arched anteriorly, and projecting very slightly over the head. The 

 pronotum is divided into lateral halves by the anterior development 

 of the mesonotum and lies partly hidden just below the humeri. 

 The mesonotum bears in this and in a few related genera a pair of 

 small sensory pits sublaterally on the humeral corners near the 



