1892.] ENTOMOLOGICAL NEWS. 227 



ON THE SO-CALLED THROAT BOT. 



By C. H. Tyler Townsend, Las Cruces, N. Mex. 



On May 15, 1892, I took a female Gastrophihis which was- 

 flying at the throat of my horse. The animal manifested unusual 

 signs of uneasiness, and I noticed the fly alight several times, 

 always exactly in the region ventrad of the first cervical vertebrae. 

 This is the so-called throat hot {Gastrophilus nasalis Lin.) of 

 whose habits but little seems to be certainly known in this country, 



G. nasalis is easily distinguishable from G. equi by its clear 

 wings, dark abdomen, and slightly smaller size. It is quite a 

 pretty species, with rust-colored pile on the scutellum and on the 

 the scutum on each side posteriorly. 



Brauer says (Mon. Oestr. 60) that "according to Dr. Green 

 G. nasalis deposits its white eggs in the region of the throat of 

 the horse." The same author says of the larva (1. c. 89): "The 

 larvae live, according to Schwab, massed together [in Haufen 

 gedrangt] in the duodenum of the horse near the pylorus [Pfort- 

 ner], seldom in the stomach. They pass out with the excrement 

 of their host and never hang fast to the sphincter internus." 

 Nothing more is said by Brauer of oviposition or habits of larvae. 



Schiner (Fauna Austr. Dipt, i, 391-2) says that "the larvae 

 live in the intestines of the horse." He also records having bred 

 specimens "from pupae which were dropped in horse-dung." 



Brauer says in his monograph that it was at that time not cer- 

 tainly known from America, but suggests Gastrus subjacens 

 Walker from Nova Scotia as a synonym. This synonymy is 

 confirmed by Osten Sacken (Cat.), who saw specimens in the 

 British Museum. Beside the above-mentioned specimen from 

 Las Cruces, N. Mex., I have two others from Kansas labeled 

 " throat bot, Sept." Osten Sacken (Cat.) says that he has seen 

 specimens from New York, Utah and Kansas. 



The peculiarity of the habits of this species in flying always at 

 the throat of the horse, with the apparent intention of oviposition,. 

 is not clear. If, like G. equi, the eggs are swallowed, why are 

 they deposited in a place so inaccessible to the mouth of the 

 horse? The animal certainly cannot get at them to swallow them 

 himself, nor have I ever seen horses biting each other in this 

 region of the neck. It would be absurd to suppose that the 

 animal could rub his throat on his fore legs in any way so as- 

 finally to get the eggs into his mouth. 



