47 



from the necks of animals which have to be on the roads. Applica- 

 tion of grease, or of oil of tar to animals. 



Related species — Simulium meridionale, the turkey gnat; Simul- 

 ium molestum, the Adirondack black-fly. It has been suggested by 

 Sambon that species of Simulium transmit pellagra of man; but 

 evidence is by no means conclusive. 



Suborder BRACHYCERA 



Family TABANIDAE, the horse fly, deer flies, et. al. Medium 

 to large size, body broad and slightly flattened; head large and 

 depressed from before to behind; eyes contiguous in the males; 

 last segment of the antennae annulate and without stylet. Females 

 provided with powerful piercing mouth-parts. Life history illus- 

 trated by : 



Tabanus atratus, the black horse-fly. Largest native species, 

 bite one of the most severe, attacks cattle more commonly than 

 horses. Eggs laid in large black masses on marsh plants. Larvae 

 live in mud or water; large, twelve jointed, cylindrical, tapering at 

 each end. Winter passed in larval stage. Pupal stage lasts but a 

 few days. Adults are not only pests, but may directly transmit 

 disease. 



Family OESTRIDAE, the bot-flies — Large, or medium size, with 

 rudimentary mouth-parts; most of the species resemble bees in 

 general appearance. Adults live comparatively short time; females 

 lay their eggs on the bodies of mammals; larvae are parasitic and 

 their development requires several months. We shall consider three 

 species : 



Gastrophilus intestinalis, (G. equi), the horse bot-fly. Adults 

 about 12-15 mm. in length, wings transparent with dark spots; 

 body very hairy, head brown, with three rows of blackish spots. 

 Eggs light yellow in color, attached to hairs of the horse, more com- 

 monly on the fore legs and shoulders. Eggs hatch in two weeks or 

 more, escape of larva being aided by licking by the horse. Taken up 

 in this way or with food they reach the stomach and attach to its 

 walls. Winter in host as larvae and following summer pass out with 

 feces; pupate in the ground and after thirty to forty days emerge as 

 adults. Bots may be so numerous in stomach as to cause marked 

 pathological changes and digestive disturbance. 



