DIPTERA. a i 
bristles on each side. Antennzw brownish red; second joint slightly tumid; third 
joint a little longer than broad, with its inferior angle rectangular; arista swollen 
at the base (which is black), the pectination long. The narrow sides of the front 
and the still narrower facial and genal orbits silvery gray, with a slightly yellow- 
ish cast; facial fovex and cheeks 
blackish, the latter clothed with 
yellowish hair. Palpi black, the 
inner surface and immediate base 
more yellowish; gently spatulate 
in shape, nearly as long as the 
proboscis and extending two- 
thirds of their length beyond the 
oral margin. Mesonotum sub- 
shining black in ground color, 
but mostly concealed beneath a 
brownish dust, which, on the 
pleure, is more grayish. Abdo- 
men with similar dust; in the 
middle with a brownish, more 
subinterrupted stripe and nar- 
row darker posterior margins to 
the segments. Femora black or 
very deep brown, first two pairs 
of tibiz and tarsi brownish yel- 
low or luteous, the hind tibize ‘ 
and tarsi blackish brown; hind > 
tibiz on the posterior surface 
with a noticeable, erect, subap- 
ical bristle; hind tarsi about as 
long as their tibiz, the first three joints widened from their base to tip, so as to form 
a distinct serration on their inner, acute angles, each of which terminates in a long 
hair. Wings with a light blackish tinge (due to microscopic pubescence), the imme- 
diate base yellowish, the first posterior cell rather symmetrically narrowed to 
terminate broadly at the extreme tip of the wing. 
Female.—Front straight on the sides, its width about equal to one-half of the dis- 
tance from the foremost ocellus to the base of the antenne; the median deep brown 
stripe about as wide as the pruinose sides. Palpi yellow, with the margins and tip 
blackish. Legs more yellowish; hind tarsi regular; pulvilli and claws small. 
Fic. 58.—Hematobia serrata: adult in resting position— 
enlarged (from Insect Life). 
The flies are observed in greatest number in July, but appear as early 
as May, and remain till cold weather, the full time depending upon the 
season or latitude. 
The characteristic habit of clustering about the base of the horn seems to exist 
only when the flies are quite abundant. When they average only a hundred or so to 
a single animal, comparatively few will be found on the horns. Moreover, as a gen- 
eral thing the horn-clustering habit seems to be more predominant earlier in the 
season than later, although the flies may seem to be nearly as numerous. The clus- 
tering upon the horns, although it has excited considerable alarm, is not productive 
of the slightest harm to the animal. Careful study of the insects in the field shows 
that they assume two characteristic positions, one while feeding and the other while 
resting. It is the resting position in which they are always found when upon the 
horns. In this position the wings are held nearly flat down the back, overlapping at 
base and diverging only moderately at tip. (See fig.58). The beak is held in a nearly 
horizontal position and the legs are not widely spread. In the active sucking posi- 
tion, however, the wings are slightly elevated and are held out from the body, not 
