30 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 
eggs upon the moist portions incubated in from 5 days to a slightly 
longer period. 
September 9 was preceded by two unfavorable days for oviposition 
and was itself very favorable, but was followed by rain and cloudy 
weather until September 15. At this time black eggs were found 
upon the dry portions of the lips, while upon the moist portions 
the eggs were reddish with whitish tips. Due to the scarcity of 
adults, the eggs were not plentiful at this time, and a few days 
later one only could be found, upon the dry portions of the lips. 
Due to the comparatively long period during which the eggs re- 
main attached upon the dry portions of the lips of horses, which is 
particularly due to the protection of the thick, coarse hairs surround- 
ing them, it is believed that one could be misled easily as to the 
most favorable places of deposition of the adults. 
GASTROPHILUS NASALIS (Linnaeus). 
SYNONYMY. 
Oestrus nasalis Linnaeus, 1761. 
Oestrus veterinus Clark, 1797. 
Oestrus salutiferus Clark, 1815. 
Oestrus clarkii Leach, 1817. 
Gastrus nasalis Meigen, 1824. = 
Oestrus duodenalis Schwab, 1840. 
Gastrophilus nasalis Schiner, 1861. 
OVIPOSITIONS AND LONGEVITY. 
The female Gastrophilus nasalis often appears from the grass 
about the fore legs of a grazing animal, strikes under the jaws, re- 
mains a few seconds, and during that time deposits an egg about 
midway upon the hair. The adult then leaves, completely disap- 
pearing in the distance, but within a minute or two a similar oviposi- 
tion may occur, except that the adult approaches from a distance. 
The presence of a person about the head of an animal does not inter- 
fere with egg deposition, and the fly may be caught with the hand 
when it alights upon the hairs underneath the jaws. It may also 
be observed to deposit upon the fore legs or the flanks. Dissections 
of the abdomen of reared females show that they are capable of 
depositing from 480 to 518 eggs. The attachment of these, as may 
be seen by referring to figure 3, c, extends to almost the entire length 
of the egg, and being attached about midway upon the hair, numbers 
are concealed unless the hair is brushed aside in making examina- 
tions. Often eggs may be observed near the end of the hairs, but 
this usually occurs after great numbers have been deposited. Then 
it is possible to find two or more eggs upon one hair. As yet the 
method of ingress of the larve has not been determined. Dr. C. H. 
T. Townsend thinks that the larve burrow threugh into the mouth 
