103 



Applications to destroy the Fly. — A great deal has been said during 

 the summer concerning the merits of a proprietary substance, consist- 

 ing mainly of tobacco dust and creosote, known as "X. O. Dust," and 

 manufactured by a Baltimore firm, as an application to cattle, and it 

 has received an indorsement from Prof. J. B. Smith, Entomologist to 

 the New Jersey Experiment Station. We are convinced that this sub- 

 stance has considerable merit as an insecticide, and know from experi- 

 ence that it will kill many of the flies when it touches them, although 

 they die slowly, and a few may recover. The substance costs 25 cents 

 per pound, and is not lasting in its effects. Where it is dusted through 

 the hair the flies on alighting will not remain long enough to bite, but 

 two days later, according to our experience, they are again present in 

 as great numbers as before. A spray of kerosene emulsion directed 

 upon a cow would kill the flies quite as surely, and would be cheaper, 

 but we do not advise an attempt to reduce the numbers of the pest by 

 actually killing the flies. 



How to destroy the early Stages. — Throwing a spadeful of lime' upon a 

 cow dung will destroy the larvae which are living in it, and as in almost 

 every pasture there are some one or two spots where the cattle prefer- 

 ably congregate during the heat of the day, the dung which contains 

 most of the larvae will consequently be more or less together and easy 

 to treat at once. If the evil should increase, therefore, it will well pay 

 a stock raiser to start a load of lime through his field occasionally, par- 

 ticularly in May or June, as every larva killed then represents the 

 death of very many flies during August. We feel certain that this 

 course will be found in many cases practical and of great avail and will 

 often be an advantage to the pasture besides. 



OTHER FLIES REARED FROM COW DUNG. 



Our observations on the life-history of the Horn-fly have been greatly 

 hindered and rendered difficult by the fact that fresh cow dung is the 

 nidus for a number of species of Diptera, some of about the same size 

 and general appearance. We have in fact, chiefly this summer, reared 

 no less than twenty distinct species of flies from horse and cow dung, 

 mainly from the latter, and six species of parasitic insects. We shall 

 give these some consideration in our final article in the annual report, 

 but can not elaborate here. The plan finally adopted to secure the 

 isolation of the Haematobias was to remove the eggs from the surface 

 of the dung and place them with dung which was absolutely fresh and 

 collected practically as it fell from the cow. Even iu tTiis way very 

 great care was necessary to prevent the occurrence of other species. 



