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. haemorrhoidalis was 
obtained. While examinations of droppings were made, most of 
the larve 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 larvee additional collections were 
made when near-by farmers came in with teams. 
In rearing adults, the larvee 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 supphed with grass sod or green foliage to 
lessen activity. Sunlight has an unusually great attraction for adult 
flies. They are very 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 larvee 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 intestations coming under his observation did 
not greatly exceed 100 larvee, and for the most part not more than 
a half dozen were to be found. 
We find the following statement by R. S. MacDougal (1899) : 
Opinion differs a good deal as to the harmfulness 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 
