158 MEDICAL ENTOMOLOGY 



there are one or two pseudopods armed with bristles or hooks. 

 On the ventral surface of the eleventh segment, and the extremity 

 of the twelvth, there are delicate finger-shaped processes, usually four 

 in number ; these are the tracheal gills. The pupa is free, and either 

 lives floating in water without any movements, or rests on the 

 bottom of the pool. It has a tuft of delicate white threads on the 

 dorsum of the thorax, which serve as breathing tubes ; or it may 

 have a pair of respiratory trumpets. 



SUBFAMILY CERATOPOGONINAE 



Small to very small flies, from 1 to 2 mm. in length, seldom 

 larger; antennae of fourteen segments, the first usually large and 

 somewhat flattened, the last five in the male larger than the others; 

 the whorls of hairs are relatively short in the female and long in the 

 male. Palpi either of four or five joints, seldom of three. Thorax 

 strongly convex, and not produced above the head. Wings flat and 

 covering each other when in repose. Costal vein ending at the 

 extremity of the third longitudinal vein ; second longitudinal vein 

 absent, and the first and third always larger and better marked than 

 the others ; third and fourth generally united by a transverse vein ; 

 the fourth, which is usually bifurcated, is not united to the fifth. 

 Legs well developed and of medium length ; femur often armed with 

 spines on the lower surface. Larva without pseudopods or long hairs, 

 or in some cases with thoracic pseudopods and with hairs. 



The following genera contain blood-sucking species : 



GENUS TERSESTHES, TOWNSEND 



Palpi three-jointed and longer than the proboscis ; first segment the 

 shortest, second segment swollen, the third straight and furnished 

 with a tuft of hairs at its extremity ; proboscis nearly as long as the head. 

 Eyes kidney-shaped, and broadly separated at the vertex ; ocelli absent. 

 The antennae of the female are inserted into large circular depressions 

 in the middle of the front, and consist of thirteen segments. 

 The first segment is the largest, and is shaped like a flattened sphere ; 

 the second is more elongate but less broad, the third to the twelfth are 

 subglobular and equal in length, and the thirteenth segment is an elon- 

 gated cone. Thorax not produced above the head, but a little broader 

 than it, and without a transverse suture. Scutellum prominent. Wing 

 studded with minute hairs ; first and second longitudinal veins better 



