GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. \) 



grenous and the source of the offensive odor. From the pharyngeal 

 walls 12 or 15 larvae were removed, 6 of which the present author 

 obtained. Three of these larvae w T ere determined as G. nasalis, and it 

 is reasonable to believe that the other larvae, which were not suffi- 

 ciently developed for identification, were of the same species. 



The larvae of G. haemorrhoidalis, "the nose-fly," as is shown in 

 Table I, may be found in the stomach, duodenum, or rectum, and 

 also attached about the margin of the anus, where they change in 

 color from pink to a greenish, become accustomed to the atmosphere, 

 and later drop to the soil for pupation. During the early stages 

 they attach within the stomach and duodenum, but later loosen them- 

 selves and reattach in the rectum, from which they gradually move 

 to the anus. The attachment of clusters of these larvae in the rectum 

 has been known to stop the passage of excreta and to cause abnormal 

 protrusions accompanied by much suffering. 



About June 1, 1915, a horse breeder in Montana experienced a case 

 of obstruction of the rectum in a yearling colt. On three different 

 occasions within one week the animal was observed lying down in 

 the pasture with the rectum greatly protruded. Each time it was 

 washed with warm water and replaced, but the larvae causing it were 

 not observed until the third time. The exact number of bots removed 

 by hand was not ascertained, but upon their removal and replace- 

 ment of the rectum the animal gradually recovered. 



Table I records a maximum of 1,032 bots removed from a 2-year- 

 old colt. The infestation consisted of 695 G. intestinalis, 218 G. 

 nasalis, and 89 G. haemorrhoidalis. This was the greatest number 

 obtained during any of the autopsies. Colts are always the most 

 heavily infested, especially when they come from summer pastures, 

 and in this case the animal was greatly emaciated, possessed a dull 

 coat, and, in spite of a good appetite and an abundance of food dur- 

 ing the previous winter, failed to grow or fatten. It had suffered 

 from a broken shoulder, the result of a kick, which ordinarily would 

 have healed promptly at this age, but instead it remained for months 

 a cripple. The owner, believing that it would never thrive, caused 

 the animal to be killed, and the post-mortem examination revealed 

 no abnormal condition, except the bot infestation and the broken 

 shoulder. It appeared that so much vitality was sapped through the 

 inroads of bot infestation that the colt had no recuperative surplus. 



At the date of the post-mortem examination 89 G. haemorrhoidalis 

 larvae had migrated to the rectum and attached. They were not suffi- 

 ciently developed to pass out and were attached at this point with 

 lesions characteristic of those usually found in the stomach. 



In Table I many of the infestations noted were comparatively 

 small when the post-mortem examination was made, and attention 

 should be called to the fact that all of these examinations were made 

 11216°— 18— Bull. 597 2 



