160 MEDICAL ENTOMOLOGY 



equal ; the empodium is well developed, and almost as long as the claws. 

 The abdomen consists of eight segments ; the male claspers have basal 

 processes without any appendages ; the terminal portion is long and 

 gradually drawn out into a point. 



All the species of this genus are small, the limit of length being 

 from 1 to 3 mm., and they are consequently not very easy to see when 

 they bury themselves among the hairs of the host ; they are easily 

 recognized, however, when they become replete with blood. They 

 often occur in large numbers, and are most frequently met with near 

 water or thick undergrowth, seldom entering houses. They attack 

 men and animals, and often cause great distress on account of their 

 numbers and of the irritation produced by their bites. Some of the 

 species show a preference for particular parts of the skin of the host, 

 feeding only from the abdomen or legs ; others select the face, and 

 especially the margins of the ears and eyelids ; only the females are 

 blood-suckers. 



The larva consists of twelve segments, including the head. Each 

 segment is contracted at both ends, and partly or entirely covered 



with spines or small protuberances: eyes are 

 Early Stages J 



absent. The antennae may be quite simple, consisting 



of a single unjointed spine-like segment, or of two or more joints. 

 On the ventral surface of the first thoracic segment there is a leg-like 

 appendage which consists of two pseudopods fused together ; its surface 

 may be smooth or covered with spines, and it is furnished at its apex 

 with simple or bifid hooks. The anal segment is armed with two ob- 

 liquely directed pseudopods, which are sometimes very short and fused 

 together, and are always furnished with hooks. The larvae often have 

 curious papillae on their dorsal surfaces, each of which may terminate in 

 a single hair or a number of spines. These structures and the numerous 

 long hairs are valuable taxonomic characters. In some forms, for 

 example, Forcipomyia, the nymph has the remains of the larval skin 

 attached to it, and in addition long hairs on its thorax and abdomen. 

 The thoracic stigmata may or may not be prominent. 



The larvae of some species are found under the barks of trees, on 

 and under decaying leaves and wood, and in sap which exudes from 

 trees ; the majority, however, live in still or running water, especially 

 where there is much algal growth, and where there are water plants, 

 such as Bromelia. In Brazil Lutz has found the larvae of several species 

 of Ceratopogon and Forcipomyia in crab holes, at the edges of mangrove 

 swamps, and below the algal crust on the sand along the seashore,: 



