126 



DIPTERA OF MINNESOTA. 



to start and strike with the fore feet, although the cause of its nervous- 

 ness is not visible. The adult fly is brownish, more or less hairy, 

 looking a little like a small honey bee. It is most skillful in depositing 

 its yellowish eggs, "nits" we sometimes call them, on the animal's 



Fig. 121. Eggs of Horse I?ot Fly, as seen under the microscope. Original. 



hairs. The moisture and friction which these receive from the animal 

 licking its hair cause them to hatch, and further licking, occasioned 

 possibly by the irritation caused the skin by the presence of the tiny 

 larvae, carries the maggot into the mouth, whence it finds its way 

 into the horse's stomach, and there completes its larval life, attached 

 to the lining of the stomach, and sometimes so abundant as to com- 

 pletely cover a portion of it, as shown in our illustration. 



Normally the egg stage lasts about fifteen days. Evidently if 

 the eggs go four weeks without being licked, a very small percentage, 

 if any of them will hatch. The bots live in the stomach or intestines 

 eight or ten months, moulting twice during that period, and naturally, 

 when numerous, sapping the vitality of the horse. They also cause 

 great irritation by attaching themselves to the lining of the small 

 intestine and rectum. In the spring these bots lose their hold and 

 pass out with the droppings ; working their way into the soil an inch 

 or two, or into some protected locality ; each "hot" or larva changes 

 to a pupa, lying within a pupal case, from which the adult fly emerges 

 after about thirty days. 



