GASTEOPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 43 



flow of repellent, which was regulated by a stopcock, moistened a 

 padded plank by means of a small pipe perforated with holes. This 

 was placed at a salting and resting place of the horses and the amount 

 of rubbing noted was very encouraging. Unfortunately, the horses 

 did not rub the corners of the mouth, which are favorable places of 

 egg deposition, and the scheme was abandoned. 



Dr. Van Es suggested the use of a repellent upon the forelegs of 

 horses and other portions of the body accessible to the mouth, so 

 as to cause the common bot fly to deposit eggs upon places where they 

 could not be reached by the horse's mouth. A marked repellent 

 quality was observed in equal parts of pine tar and lard, no adults 

 having been observed to oviposit during the following 4 days. There 

 was apparently no injury to the animal, and 1 part of tar to 2 parts of 

 lard was effective during 3 days. The disadvantage in some of the treat- 

 ments was the fact that animals would walk through mud and water 

 and cause a decrease in the repellent qualities of the mixture applied. 

 Very good results were obtained with pine tar 3J ounces, kerosene 

 1J ounces, laundry soap 1 ounce, powdered resin 1 ounce, and hot wa- 

 ter to make 14 ounces. The pine tar was thinned with kerosene, the 

 soap and resin dissolved in hot water, and the two mixtures poured 

 together. There was not only great repellent action observed, but 

 the resin caused the hair to stick together in small bunches and pre- 

 vented the adult flies from ovipositing. There was apparently no 

 injury to the skin of the animal, and these same repellents pre- 

 vented G. nasalis from ovipositing under the jaws. A successful repel- 

 lent that would not require renewal over a reasonable period is de- 

 sirable, since the loss of time due to the renewal of repellents is a 

 great loss. 



MECHANICAL PROTECTIVE DEVICES FOR WORK HORSES. 



The protective devices found upon work animals vary, but there 

 are none used in the Dakotas on pastured animals. (See Plate V.) 

 Various forms of fringes are most frequently found and may consist 

 of leather, burlap, or a portion of the leg of trousers. These are 

 probably the least effective of the devices, as examination of teams 

 wearing such fringes developed the fact that they are often found 

 infested with eggs. Leather seems to be the most efficient of the 

 fringes, as it is not so easily blown aside by the wind and does not 

 hinder the horses in breathing. Those extending completely around 

 the head retail for 50 cents each, while those covering only the face 

 sell for 25 cents. 



Baskets which are used extensively in nose-fly districts serve as 

 muzzles during the last plowing of corn, but are not very effective 

 nose-fly protectors. The mesh is of sufficient coarseness to permit 

 flies to oviposit if the lips can be touched. They do not always fit 

 well at the top and occasionally a nose fly will get on the inside, 



