24 PARASITOLOGY. 
HEMATOBIA SERRATA (Hema—blood; bios—life; serra—saw. ) 
Synonyms.—Horn-fly; saw-fly. 
History.—It was introduced into this country in 
1887 by an importation of cattle from Europe. It 
first appeared around Philadelphia, and in a few 
years was found in all parts of the country. 
Description.—A small black fly, about one-third 
the size of the common house-fly. When at rest 
the wings are nearly parallel with the body. 
The head is provided with a proboscis for sucking 
blood. 
Lite Cycle.—The flies appear with warm weather, 
and die with the frosts of autumn. The eggs are 
oval in shape and brown in color, and are laid in the 
fresh feces. Theeggs are nearly straight along one 
side and the larva emerges from the shell by raising 
a long, ribbon-shaped strip at this side. The ovum 
hatches in about twenty-four hours. The larvae 
reach their fully developed stage in about five days. 
They then burrow into the ground about half an 
inch, where they pass the pupal stage, which lasts 
about eight days. 
Animals Attacked.—Cattle are most often attacked, 
the flies attacking them in large swarms, burying 
themselves in the hair and sucking the blood. In 
rainy weather they are found to attack the animal 
under the belly. At night they may be found in 
clusters around the horns. 
Conditions Produced.—The constant harassing of 
the animal by large numbers of the flies causes milch 
cows to fall off in the yield of milk. Fattening and 
other animals do not thrive. 
Treatment.—Fish-oil and tar, equal parts, will keep 
