HORSE BOTS 



How To Control Them 



Three species of horse bot flies are 

 serious pests in this country. 



The common bot fly and the 

 throat bot fly occur throughout the 

 United States. The nose bot fly is 

 found in Northwestern and Mid- 

 western States. 



Bot flies can be controlled by 

 treating infested animals to destroy 

 larvae and eggs. 



HOW BOT FLIES LIVE 



Bot flies have four life stages — 

 adult, egg, larva (bot), and pupa. 

 These stages are described on this 

 page and on pages 4 and 5. 



Adult flies do not feed. Their sole 

 purpose in life is to reproduce. They 

 live from a few days to 3 weeks. 



In Northern States, flies appear 

 about the middle of June ; they live 

 until there is a heavy freeze. In 

 Southern States, they appear as 

 early as March and may be seen 

 until December. 



Eggs usually can be found on 

 horses as soon as flies are seen. Egg 

 laying continues as long as adults 

 are present. Eggs of the common 

 bot fly that can hatch may be found 

 on the animals as late as December 

 in Northern States, and as late as 

 February in Southern States. 



During the larval stage, the bots 

 develop inside the animal; they 



grow from minute size to about two- 

 thirds of an inch in length. The 

 exact nature of the food they take 

 is not known, but bots feed on body 

 fluids. 



Mature bots may be found in the 

 digestive tracts of horses and other 

 equines at any time of the year, but 

 they usually pass out of the animals 

 by October. Practically all the bots 

 found in animals during the early 

 part of the winter are young. 



When fully developed, bots pass 

 out of the animal to the ground, 

 where they seek protection. They 

 crawl very little. Usually they bur- 

 row into the ground near the place 

 where they were dropped. They 

 burrow only deep enough to escape 

 the direct rays of the sun. 



COMPARISON OF THE 

 THREE SPECIES 



Common Bot Fly 



(Gasterophilus intestinalis) 



Adult. — Largest of the three 

 species; about the size of a honey 

 bee. Body is covered with black and 

 yellow hair. Wings are mottled. 



Female hovers about animal; 

 darts from place to place as she 

 cements egg after egg to hairs on 

 the forelegs (a favorite place), the 



