28 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 
the stalk hag never been observed to be inserted for its full length. 
Often it extends to such a slight depth that after a few days the egg 
may be found lying lengthwise upon the lips, yet firmly attached to 
the hair. The color, a jet black, so conceals the attachment to the 
transparent hair that it appears that the hair extends through the 
center of the stalk portion and through a portion of the side of the 
egg. The extreme point, however, shows a folding about the hair 
which may be attributed to the pressure when it is inserted in the 
pore of the skin. Above the stalk portion the hair is attached to 
the side of the chamber containing the larva in a similar manner to 
the attachment of other Gastrophilus eggs upon the hair. 
INCUBATION AND INGRESS OF LARVA. 
Having observed eggs upon both moist and dry portions of the 
lips of horses, large numbers in various stages of incubation were 
removed and placed in tubes for observation. About 100 were kept 
in a test tube, with a moist cotton stopper, at the air temperature 
of a living room. While a variation in color was at first observed, 
ranging from a black to a reddish color, after a few days the major- 
ity were of a reddish brown. Some were placed upon a slide and 
moistened, then by the use of two dissecting needles dead larve were 
removed. No larve had hatched of their own accord, but emerged 
when subjected to moisture and friction. In similar tubes which 
were kept dry three lots of eggs varying in color were observed and 
not a single larva hatched. 
Examinations of the inside of horses’ lips revealed numerous holes 
accompanied by much soreness which appeared as though the young 
larvee hatched and had burrowed through the lips. Upon dissec- 
tions in post-mortem examinations it was disclosed that the injury 
was caused by “wild barley” or “foxtail grass.” This grass was 
determined by the Bureau of Plant Industry as Hordeum jubatum. 
Its injuries are more noticeable upon lips of livery horses when fed 
hay containing this grass. as pastured animals avoid eating it and 
the injury is less noticeable. It is worthy of note that this grass, 
in addition to its injury upon lips of horses, serves as a winter host 
of the black rust which is so destructive to wheat in the Dakotas. 
On August 24, 1915, a suckling colt, its mother (a crippled horse) 
and another horse were carefully freed of eggs. Twenty-four hours 
later a diagram was made showing the exact location of each ege 
deposited during this time. Upon the following three days it was 
too cloudy for other adults to oviposit, so the horses were not kept 
in a barn to prevent further ovipositions, but were left to graze in 
the pasture. This allowed ample time for development of the 
embryo and of a distinguishing brownish-red color which greatly 
aided in keeping track of the eggs. 
