THE FLIES 41 



mixed considerable straw affords a favorable medium for the propaga- 

 tion of this fly, — a further reason for its systematic removal to be at once 

 spread upon the fields, as stated in control measures for the house fly. 

 It should be borne in mind, however, that stables are not predominant as 

 breeding places of the fly under consideration, as is the case with the 

 house fly. Stomoxys is attracted to stables because the animals from 

 which it obtains its meal of blood are contained there. The favorite 

 material for the deposition of its eggs is likely to be found elsewhere. 

 These flies like the open, and districts far from stables may be overridden 

 with them. 



Protection. — Little can be done in the way of direct protection of 

 live stock against the attacks of stable flies beyond thorough screening, 

 the effectiveness of which is much lessened by the frequent opening of 

 doors customary about stables. Means of keeping them out should be 

 especially looked to in cloudy, damp weather, and in the cool mornings 

 of early autumn, at which times they are most likely to seek the interior 

 of stables and houses. 



Lypekosia Irritans 



Hcematobia serrata. — The horn fly (Fig. 23). Muscidse (p. 37). About 

 half as large as the house fly and like it in shape and color. The mouth 

 parts are adapted for piercing and sucking blood, but differ from those 

 of the stable fly in that the palpi are almost as long as the proboscis and 

 are sUghtly spatulate. 



The eggs (Fig. 23, a) are about 1.25 mm. in length, irregularly oval, and 

 reddish brown in color. They are deposited in the fresh dung of cattle, 

 and, imder favorable conditions of temperature, will hatch in about 

 twenty-four hours. 



Life History. — Newly hatched larvae are about 2.5 mm. in length, 

 and pure white. When full grown they are about 7 mm. in length and 

 somewhat darker in color. The larvae burrow into the dung and reach 

 their full growth in about four days (Fig. 23, b). When ready to trans- 

 form into the pupal stage the larvae descend into the dryer parts of the 

 dung, or for a short distance into the ground beneath it. The puparium 

 (Fig. 23, c) is about 4.5 mm. in length, irregularly elhpsoidal, and dark 

 brown in color. The pupal stage occupies from five to ten days, therefore 

 the time for full development from the deposition of the eggs will be, 

 according to the above, from ten to fifteen days. 



Occurrence and Habits. — The horn fly is an importation from 

 Europe, making its first appearance in the vicinity of Philadelphia about 

 the year 1886. It was first noticed as a pest to cattle in this country in 

 1887, from which time it has spread rapidly and at present is found in 

 practically all parts of the United States and the greater part of Canada. 



The popular name "horn fly" is derived from the habit peculiar to 



