14 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 
proceeds from infuriated shaking of the head, sometimes accompanied 
by loud snorts, to complete loss of self-control, and will use any 
means for self-protection. Numerous runaways naturally occur and 
serious accidents have also occurred when horses were being used 
for mowing. The majority of farmers and breeders contend that 
“the fly stings the horse in the nose.” The reactions of the animals 
are often so violent that at first it seemed that the horses really 
experienced pain. Dr. Parker, of the Montana State Board of 
Entomology, has published some notes? to the effect that the eggs 
were thrust into the skin, but he failed to recognize the minute hairs 
to which the eggs are attached. The poinied portion of the egg is 
merely a device by which it is attached to the hair. A horse does 
not experience any pain, as the ovipositions do not puncture the skin. 
Neither. do the flies deposit in the nostrils. Careful search has 
failed to disclose a single egg in such locations, and it would appear 
that the snorting of the animal has given rise to this “ popular 
opinion.” It is believed, however, that annoyance is largely due at 
first to an instinctive fear and later to a tickling sensation when the 
eggs are attached to the minute hairs, as the lips are the most sensi- 
tive portions of the horse. Practically all horses in this section have 
sore lips from eating a “ wild barley” or “ foxtail grass” (Hordeum 
jubatum) and there is no doubt that this soreness contributes to 
the annoyance. 
NATURAL PROTECTION OF HORSES. 
The flies show no preference as to type, breed, color, or age, but 
naturally oviposit upon unprotected animals. Horses seek protection 
in pastures, the individuals gathering in a bunch and resting their 
lips upon one another. Colts and young animals not high enough 
to protect their lips in this way receive an abundance of eggs. 
A horse will sometimes hold the lips upon the ground as if grazing, 
upon detecting the presence of the fly, and when held in such posi- 
tion the adult fly is rarely observed to oviposit. Often the annoyance 
of biting flies and other depositing Gastrophilus will cause a horse 
to walk, holding the lips near the ground. Frequently other horses 
will follow and protect themselves by placing their lips upon his 
back or the backs of other animals in the line. Usually they search 
for the highest elevation where the breeze is blowing, or for standing 
water, but if an open stall is convenient they will use it to good 
advantage. If protection is not found an unconfined animal will 
often wander a great distance from home. 
Upon a bright still day ovipositions occur from 8 a. m. until about 
sunset, and the group of horses may be observed to shift from place 
1 See “ Bibliography,’ page 50. 
