MOSQUITOES AND GNATS 31 



Effect upon Live Stock. — That mosquitoes are a source of much 

 annoyance and actual suffering to live stock can be attested to by stock- 

 men. Horses and cattle pasturing upon low lands and amid vegetation 

 where the insects abound are especially exposed to attack, the pests 

 often hovering about them in clouds, while upon the bodies of the 

 animals large numbers may be seen with abdomens engorged with the 

 blood of their victims. Loss of condition and the falling off of produc- 

 tiveness in dairy herds must essentially follow this interference with 

 their pasturage and comfort. 



Control. — The most effectual preventive measures dealing with mos- 

 quitoes are those directed against the larvte. The abolition of breeding 

 places being of first importance, all receptacles for standing water, such 

 as rain barrels, cans, vaults, gutters, etc., should be removed, covered, or 

 otherwise made impossible to access and propagation of mosquitoes. 

 Pools should be drained, or, if this is not feasible, may be treated with 

 kerosene; or small fish, which feed upon the larvae, may be introduced 

 into the mosquito-breeding ponds. The quickest and most satisfactory 

 way to destroy larvae and pupae is by the formation of the kerosene 

 film upon the water's surface. The oil is best applied for this purpose 

 as a spray, or, if but a small area is to be treated, it may be thrown upon 

 the surface and the water then vigorously stirred. About one ounce of 

 kerosene to fifteen square feet of water surface will be sufficient, and this 

 application should be repeated at intervals of about three weeks. 



Such measures are directed only against local species, and, essentially, 

 there must be community action for it to be effective. Migratory forms, 

 such as are bred in the marshes near our coasts, cannot thus be reached, 

 their eradication constituting a problem demanding state control. 



For indoor protection in mosquito-infested districts, screening is of 

 course essential. In spite of the most thorough screening, however, 

 mosquitoes will enter in various ways, as through opening doors and upon 

 the clothing of persons passing in. As remedies against those which 

 have gained access to houses various kinds of repellents are used. Burn- 

 ing pyrethrum powder will often rid a room of mosquitoes, a convenient 

 method being to sprinkle the powder upon a heated shovel; or small 

 cones may be molded from the dampened powder and, after drying, 

 burned. Oil of pennyroyal or citronella applied to handkerchiefs or 

 lightly touched to the hands and face, though objectionable to some, 

 will usually insure a peaceful night against the pests. 



Family II. Simuliid^ 



Diptera (p. 23). The flies of this family are known as black flies, 

 black gnats, or buffalo gnats, the latter name derived from their pecuhar 

 humpback appearance. They are dark colored, with short thick body, 



