TWO SPECIES CONFUSED 319 



ently made for the purpose of respiration, discharge of excremen- 

 titious matter, and the final escape of the bot (Fig. 324). 



Injury. The bot or larval stage lasts for nine or ten months, 

 and the vital activities of the bot, if abundant, cause the victim 

 to lose flesh, to fall off in milk if it is a milch cow and impart 

 to the flesh in the vicinity of its work a slimy, greenish appearance. 

 This abnormal flesh is called "licked beef" by butchers. 



When mature, the bots force their way through the hide and, 

 dropping to the ground, bore an inch or so into the soil, turn into 

 pupse, and after about four weeks in the pupal stage emerge as 

 perfect flies. Until 1890 it was supposed that the eggs were laid 

 on the back of the animal, and that the maggots penetrated the 

 skin at that place. 



Two Species Confused. Hypoderma bovis De Geer is the 

 most commonly described ox-warble fly, but it is doubtful whether 



FIQ. 324. Vertical section of hide and subjacent tissue showing ox warble in position. 

 Diagramatic. (Courtesy of Country Gentleman.) 



this species is found in the United States. Probably the injury 

 to stock that suggests this insect should be ascribed to the striped 

 warble fly, or heel fly (Hypoderma lineata Villers) . This is a hairy 

 fly (Fig. 325) which looks a little like a dark-colored bee. There 

 are yellowish-white hairs on the thorax, while above, the abdo- 

 men is banded with black and whitish color. Four lines on the 

 thorax give it its name, the striped warble fly. The name "heel 

 fly" comes, according to the statement of cattle men in the 

 Southwest, from the fact that it lays many eggs on the heels of 

 the cattle, above the hoofs. The eggs are attached to the hairs 

 by a peculiar clasping apparatus at one end. 



Control. These tumors may be easily detected, when present, 

 by running the hand over the back of an animal. The bot may be 

 squeezed out of the tumors on the back of milch cows and killed. 

 To do this, enlarge the opening a trifle, if necessary, with a clean 

 knife. This squeezing out of the bots causes some pain, as is 



