DIPTERA of MINNESOTA. 133 



and about the nose the following compound : Pine tar, two parts, fish 

 oil or cotton s'eed oil, one part, powdered sulphur one part. Some, 

 instead of using salt logs, plow a few furrows across the pasture, into 

 which the sheep may stick their noses when attacked. Some breeders 

 keep deep dust in a portion of the sheep yard, into which the animals 

 instinctively thrust their noses when attacked by the fly. This, how- 

 ever, only affords temporary protection, since the fly returns to the 

 attack as soon as the animals leave the furrow. All modern books 

 on sheep raising undoubtedly contain the latest and best remedies for 

 all parasites of sheep. One or more good books of this kind should be 

 in the hands of every sheep raiser. 



OX BOT FLIES, WARBLE FLIES. 



The genus Hypoderma includes species of bot flies which make 

 tumors on cattle, and while not very abundant in Minnesota, their 

 presence on our dairy cows or beef stock, even in limited numbers, 

 makes them of special interest. Like other bot flies, they lay eggs on 

 the hairs in spring and summer, and these eggs are either hatched by 

 the moist friction of the tongue of the animal, the tiny maggots finding 

 their way into the mouth by subsequent licking, or the eggs themselves 

 are carried into the mouth and hatched there. In this event the young 

 maggots migrate down the gullet, through its walls and other 

 tissues of the victim, until they reach the skin, where (generally some 

 time after Christmas) they appear, forming the swellings known as 

 "warbles". Here, in tumors caused by their own activities, they 

 mature, their anterior end, with its mouth, being at the bottom of 

 the tumor, where the mucus upon which they feed gathers, and the 

 posterior end, through which most of the breathing takes place, is 

 directed upward, and is near the small opening in the hide, apparently 

 made for the purpose of respiration, discharge of excrementious 

 matter, and the escape of the bot. These holes are also called 

 "warbles". 



This bot stage 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 imparts to the flesh in the 

 vicinity of their work a slimy greenish appearance. This abnormal 

 flesh is called by butchers "licked beef". When mature the bots force 

 their way through the hide, and dropping to the ground, bore an inch 



