660 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



are the large Black Horse Fly (Tabanus atratus Fab.), which is 

 the largest form commonly seen and particularly abundant in 

 wooded sections where its vicious biting and bullet-like flight 

 make it quite conspicuous; a slightly smaller grayish-brown some- 

 what striped species is nearly as large and is found on cattle more 

 frequently than is the preceding; and the several smaller kinds 

 'with green eyes, suggesting the common name Greenheads, 

 (Tabanus lineola Fab. is one), which attack by preference the ears 

 of horses and do not hesitate to attack man. 



Larvae of horse flies are cylindrical maggots, pointed at both 

 ends, which live in ponds and marshes. 



Little can be done to eliminate the horse flies, or gad-flies as they 

 are sometimes called. Fly-nets, with ear-nets attached are much 

 more useful for these than for the smaller flies which attack animals. 



The Screw Worm Fly* 



In the southwest an important insect pest of livestock, par- 

 ticularly range animals, is a maggot or screw-worm, the larva of a 

 fly intermediate in size and appearance between the common house 

 and stable flies and the green-bottle flies. The distribution of the 

 insect includes the territory from the lakes to the gulf, but it is a 

 serious problem only in the South and Southwest. 



The injury is the result of the work of the larvae in the flesh of 

 the infested animals. Eggs are deposited by the adults in wounds 

 or often even on exposed mucous membranes. The larvae upon 

 hatching burrow in the flesh and cause inflammation and mechanical 

 injury followed by infection and the sores refuse to heal without 

 treatment. Wire-cut animals, saddle-galled horses, and range 

 cattle at the time of calving, offer conditions suitable to attract 

 these flies. Injury to man is not uncommon, the eggs being usually 

 deposited in the nostrils during sleep and the larvae working their 

 way up into the nasal passages. Children are the most frequent 

 sufferers. 



The extent of the injury in the infested regions is hard to esti- 

 mate but it is certainly great. The flies breed in decaying animal 

 matter as a rule, the infestation of living animals being only an 

 occasional habit for the species. 



* Chrysomyia macellaria Fabr. Family Muscidce. See Bishopp, Mitchell 

 and Parman, Farmers' Bulletin 857, U. S. Dept. of Agr. 



