228 EMASCULATING-FLY. 
to some a few words about them willnot comeamiss, though 
these flies do not injure our domesticated animals. Fig. 184, 
explains itself. The host isa striped gopher, which harbored 
three of these bot-flies, two smaller ones and onealmost fully 
grown. The tumors made by the large one and by one 
of the smaller ones are shown; they are under the skin 
and each communicates with the outside by means of an 
opening. Against these openings were pressed the anal ends 
of thelarvee, which contained the breathin g-organs. Thethird 
larva was found in the neck of the gopher. The old story 
told by hunters that mature male squirrels are in the habit of 
emasculating the younger ones, for very selfish reasons, finds 

Fig. 185.—Adult of emasculating-fly. Enlarged. Original. 
thus a more natural explanation. Some years ago the 
writer observed a fly belonging to the above genus leaving 
the burrow of a striped gopher. Though it is not wise to 
jump to conclusions, we may take it for granted that this fly 
is the adult of such emasculating bots. It is illustrated in 
fig. 185. As seen by the line giving the size of the insect it is 
a large fly, with a black face free from hair, large red eyes, a 
polished black thorax covered on the sides with long yellow 
hairs, the scutellum is covered with short black hairs, the 
abdomen is polished, of a dark steel-blue color, and sparsely 
covered with short black hair; only the penultimate 
