31 



to dwell in the nostrils about ten months. This statement has not yet 

 been verified. In very young lambs only young larvtB can be found, 

 while in yearlings the larvse may be nearly adult, depeudiug on the 

 exact age of the iamb and the time it was infected. In yearlings the 

 frontal sinuses are small and the grubs easily escape detection. It is 

 in two-year-olds and older sheep that one finds the greatest infection. 

 In ewes the sinuses are sufficiently roomy to hold four or five larvae 

 without crowding, but wethers, which have small horns, or bucks which 

 have very large frontal sinuses, can harbor many more. Earely have 

 more than six or seven been found. Cases have been reported in otlier 

 countries where far larger numbers, as many as ten to fifteen, were 

 found. The largest recorded number seems to be from sixty to eighty. 

 The relatively small number discovered, and the comparatively large 

 size of the young when deposited, indicate that each female lays but 

 few young. It is very unusual to find more than two or three larvae of 

 the same size, especially if they be mature or nearly so. The young 

 larvae are sometimes more numerous, six or seven of nearly equal size 

 being found together. The presence of all sizes of larvae in the cavi- 

 ties is Q, plain contradiction to the statements made that the Q.y appears 

 only in June and July, for, no matter whether it takes ten mouths for 

 the larvae to grow or not, young and middle sized and mature larvae 

 found in the winter time could not all have been laid within the two 

 months indicated. 



The more correct statement is that the fly may appear at any time 

 when the temperature is not too low, but that they are more abundant 

 in early and midsummer. 



Freventive treatment. — Most authorities on this subject recommend 

 preventive measures, but practical application of the means and reme- 

 dies proposed is necessary to demonstrate their utility. A change of 

 pasturage or an avoidance of brush-fields does not seem to be advisa- 

 ble unless the sheep are turned into longer grass, for the flies are able to 

 follow the sheep wherever they may go. 



A practical means of prevention consists in smearing the noses with 

 a mixture of equal parts of tar and grease, or of tar and fish-oil, or of 

 tar and whale-oil. The better way is to apply the preparation directly 

 by a brush. Some recommend smearing the salt and grain troughs with 

 the mixture, expecting the sheep while feeding to get more or less on 

 the nose. This method is not thorough enough. Fish or whale oil 

 alone is also recommended. Powers (American Merino, 1887, p. 300) ad- 

 vises the following ointment for this purpose : Beeswax, 1 pound ; lin- 

 seed-oil, 1 pint ; carbolic acid, 4 ounces. Melt the wax and oil together, 

 adding 2 ounces of common rosin to give body, then, as it is cooling, stir 

 in the carbolic acid. This should be rubbed over the face and nose once 

 in two or three days during July and August. He also recommends an 

 apparatus which may well be used by owners of first-class breeding 

 gtock, and possibly others who own but few sheep : " A canvas face- 



