30 



CIRCULAR 14 8, U. S. DEPARTMENT OF AGRICULTURE 



as possibly of use, but less on account of this parasite than for other 

 reasons. 



BOTS 4 



Bots are maggots of certain flies (fig. 22) known at botflies. Three 

 species of bots commonly occur in horses in the United States. 



The common botfly, GastrophUus intestinalis, occurs in practically 

 all parts of the United States. The bots, or parasitic larvae, are reddish 

 in color and are attached to the white covering of the left sac of the 

 stomach or along the ridge between the right and left sacs of the 

 stomach. The adult fly deposits its eggs on the hairs of the inside of 

 the front legs, breast, mane, belly, and even the hind legs. The throat 

 botfly, or chin fly, G. nasalis, is rather widely distributed in the United 



l 



■Mi 



Figure 22. — Portion of a horse's stomach, showing bots, GastrophUus intestinaUs, 

 attached to the inner lining of the stomach wall. Natural size 



States and is especially common in the Rocky Mountain region. The 

 adult fly of this species deposits its eggs under the jaw of the horse, 

 and in so doing causes much annoyance to horses. The bots are yellow- 

 ish in color and are attached to that portion of the stomach which joins 

 the small intestine and also to the wall of the upper part of the intestine. 

 The nose fly, G. hemorrhoidalis, has a more limited distribution than 

 the other two species and is mostly confined to the North Central 

 States and certain of the Rocky Mountain States, but it is spreading in 

 all directions. The adult flies of this species deposit their eggs along 

 the edge of the lips and cause much annoyance to horses. The nose fly 

 is the most dangerous of the botflies and is the one which is responsible 

 for many accidents because its annoyance makes horses panicky and 



4 For more detailed information concerning horse bots and their prevention consult 

 Farmers' Bulletin 1503, The Horse Bots and Their Control. 



