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. 



Life 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. The eggs 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. 



Aftimals 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. 



Conditio7is 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. 



Treatinent. — Fish-oil and tar, equal parts, will i^eep 



