6 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 



be observed, and at the same time easily accessible to a rendering 

 plant where post-mortem examinations could be made. Horses in 

 pasture were available in all directions, and livery barns were located 

 within a mile and could be conveniently visited. 



Horses of many types, representing every locality in the imme- 

 diate vicinity, could be observed in the livery barns, and it was 

 from these horses that breeding material of G. haemorrkoidalis was 

 obtained. While examinations of droppings were made, most of 

 the larvae utilized were removed from their places of attachment 

 about the anus. These were sufficiently developed to pupate and 

 produce adults, and did so even though they were not handled care- 

 fully with the forceps in removal. The number of horses in the 

 liveries varied, but usually from 30 to 100 were observed daily. In 

 order to obtain an ample supply of larvae additional collections were 

 made when near-by farmers came in with teams. 



In rearing adults, the larvae were placed in tin boxes upon moist 

 sand in California parasite-rearing boxes, or in bread trays upon 

 grass sod. These were usually kept in cages 18 by 18 by 18 inches, 

 each of which was fitted with a door of sufficient size to permit the 

 removal of trays for examination. When adults emerged it was 

 necessary to confine them in tightly fitted cages which excluded sun- 

 light, and to keep them supplied with grass sod or green foliage to 

 lessen activity. Sunlight has an unusually great attraction for adult 

 flies. They are ver}^ active and will damage their wings against 

 the screen or crawl into a cage crevice and die. More especially has 

 this been noted with G. haemorrhoidalis. 



LARVAL INFESTATION AND INJURIES. 



REVIEW OF OPINIONS. 



In reviewing opinions on the economic importance of bot-flies, 

 one naturally encounters the ideas of Bracy Clark, which have been 

 passed from one to another since 1798. He believed that larvae by 

 irritating the membranes of the stomach and intestines often re- 

 lieved a general disorder of the system, but mentions that, however 

 useful a few of these natural stimuli may be, they result in large 

 infestations which should at all times be prevented. He indicates 

 in this paper that the infestations coming under his observation did 

 not greatly exceed 100 larvae, and for the most part not more than 

 a half dozen were to be found. 



We find the following statement by K. S. MacDougal (1899) : 



Opinion differs a good deal as to the liarmfulness of these bots. In conver- 

 sations with veterinary surgeons I find there is a tendency to minimize the 

 evils that may attend bot presence. There are authenticated records, however, 

 which place the possibility of grievous harm beyond all doubt. Inflammation, 

 ulcers, interference with digestion, interference with the free passage of food 

 or exit of waste matters, loss of appetite and condition, have been frequently 



