40 PARASITES OF THE DOMESTIC ANIMALS 



pupal stages. Development with the appearance of adult flies will 

 occur in warm stables during this season. 



Occurrence and Effect. — The stable fly is of world-wide distribution, 

 and is commonly mistaken for the house fly, the term "biting house 

 fly" being often applied to it from its habit of entering our houses during 

 damp, rainy weather and in the cooler days of early autumn. It may 

 quickly be distinguished from the common house fly, however, by its 

 elevated head when at rest, its protruding, bayonet-like proboscis, and 

 its wings, which are widely spread apart at the tips. 



Though commonly called the stable fly, Stomoxys is found in far less 

 numbers about stables than is the house fly, and, as it will not visit such 

 filth as does the latter, it is not such an ofl'ender against the cleanliness 

 of dairy and other food products. Both sexes of Stomoxys, however, 

 are vicious blood-suckers, and their bite is especially a source of torture 

 to thin-skinned, sensitive animals. Typically an out-of-door fly, it is 

 most hkely to enter stables in the cooler days of late summer or early 

 autumn when it will attack horses and cattle, attaching itself by prefer- 

 ence upon the legs. Their sharp sting is manifested by the stamping, 

 kicking, and general restlessness of the victims. The punctures are 

 often followed by the formation of papules which may coalesce and 

 rupture, leaving a scaly, more or less thickened skin with hairs scant, 

 lusterless, and erect. To the dairy they are a source of loss in milk 

 production through the worry and unrest caused by their attacks. 



Relation to Disease. — The possibilities of the stomoxys fly as a 

 disseminator of infectious diseases have in recent years received con- 

 siderable attention. Its habit of visiting a number of hosts before 

 becoming engorged with blood, together with its deep puncture, war- 

 rants us in charging against this species possibilities in the transmission 

 of anthrax in cattle and glanders in horses. By some authors it is re- 

 garded as a carrier of the trypanosome [Trypanosoma evansi) which 

 produces surra of horses. Of this, however, there is no conclusive experi- 

 mental evidence. As to the responsibility of the stable fly for the spread 

 of infantile paralysis, it will be sufficient here to quote Riley and Johann- 

 sen, who, after reviewing the evidence, thus state their conclusions 

 (1915): "The evidence at hand to date indicates that acute anterior 

 poliomyelitis, or infantile paralysis, is transmitted by contact with 

 infected persons. Under certain conditions insects may be agents in 

 spreading the disease, but their role is a subordinate one." 



Control. — Control measures consist in removing materials which 

 afford favorable breeding places for the fly. Collections of moist and 

 fermenting feed material, such as have been mentioned, should be re- 

 moved and scattered in a layer sufficiently thin to insure thorough 

 drying. It will then be unsuitable for the development of stomoxys 

 larvse, as they require considerable moisture. Manure in which there is 



