. Bulletin of the Department of Agriculture. Agriculture; Agriculture. BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. upon the flanks or forelegs of the animal. Unlike G. intestinalis, it does not remain near the animal prior to the deposition of a second egg. G. haemorrhoidalis is easily distinguished by the bright orange red on the tip of the abdomen. The thorax above is olive gray and hairy, with a black band behind the suture. The base of the abdo- men is whitish and the mid- dle blackish, which is in strange contrast with the orange red of the end. It deposits only upon the small hai
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. upon the flanks or forelegs of the animal. Unlike G. intestinalis, it does not remain near the animal prior to the deposition of a second egg. G. haemorrhoidalis is easily distinguished by the bright orange red on the tip of the abdomen. The thorax above is olive gray and hairy, with a black band behind the suture. The base of the abdo- men is whitish and the mid- dle blackish, which is in strange contrast with the orange red of the end. It deposits only upon the small hairs on the lips of horses and mules. The males of G. intesti- nalis and G. haemorrhoi- dalis are often found await- ing the approach of females to the horses, and when they arrive the flies copulate. The species characteristics of the eggs of the three species occurring in the. Fig. 2.—Gastrophilus haemorrhoidalis: Female. Oviposits only upon the small hair on the lips of horses, preferably the portions moistened by saliva. Greatly enlarged. (Original.) United States can best be observed by referring to the illustration (fig. 3). While G. intestinalis is usually attached about one-half its length to the hair, G. nasalis is attached almost its entire length. G. haemorrhoidalis is always found attached to the base of a hair on the lips. These hairs are so small that one does not observe them with the naked eye. It is the only Gastrophilus depositing here. The egg is black in color and the stalk is partially inserted in the pore of the skin at the root of the hair. Fourth-stage lavse, as can be seen in the illustration (PL I), vary in size when fully developed. In all specimens the eleventh ring is completely deprived of spines, but upon the other rings the varia- tions are often misleading. However, the key given herein will assist in identifying fully developed larvae. Key for the Identification of Fully *Developed Larvae of Gastrophilus spp. 1. Spines arranged in two alternati
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