8 July, 1908.] Diseases of flic Skin. 445 



Tobacco water and arsenic solution will also kill them, but watery solu- 

 tions do not blend with the greasy wool and skin, and hence they do not 

 penetrate sufficiently far. I'he drawback to curative treatment, however, 

 is that there are usually successive invasions of the fly, because the old 

 scalded spot or wound is in suitable condition for the deposition and 

 development of successive " blows," so that the treatment involves a lot 

 of trouble, and may have to be continuously repeated. Such repetition 

 of treatment is practically impossible on extensive sheep runs, and it is 

 impracticable in a large number of cases to apply medicinal agents even 

 once. Many of the sheep are never seen for days together, and it hence 

 becomes the supreme object to procure the prevention of the attack of the 

 fi\. Almost any substance with a pungent aroma — kerosene, eucalyptus 

 oil, oil of rue, phenyle, creolin, tincture of assafoetida, and the like — 

 will deter the fly, but their effects are usually evanescent. There is one 

 substance, however — fish oil — the foetid aroma of which persists for 

 months, and it is said that a few drops of it sprinkled on the wool in the 

 region of the !tail will prevent the attack of flies throughout the season. 



The fish oil recommended is the ordinary fish oil of commerce pro- 

 curable from any wholesale chemist. It is sometimes sold under the 

 name of train oil. When freshlv prepared it is comparatively clear oil, 

 dark brown in colour, and non-volatile, but later on it may develop floccu- 

 lence or sediment. The disagreeable penetrating and persistent odour also 

 increases the longer it is kept on account of the development in it, by 

 oxidation of the oil, of a substance called valerianic acid. oiV which its 

 odour depends, and w'hich is also present in minute quantities in decaying 

 cheese. It is this quality or power to keep on forming the stinking and 

 acrid valerianic acid when exposed to the air which renders it superior 

 to most other substances as a deterrent of flow -flies. As the odour 

 volatalises it is replenished, so to speak, by further formation of acid, 

 and so long as traces of the oil remain in the wool — and the oil itself does 

 not volatilise or dissipate readily — so long will the odour persist and deter 

 attacks of the fly. 



Another dressing that has been used with success in keeping the sheep 

 to which it was applied free from attacks for the season is — One part' 

 crude carbolic acid crystals dissolved in fiftv yiarts of crude vaseline. To 

 this mixture add one part sulphur to two parts of the mixture. In this 

 case it is probably the gradual decomposition cf the sulphur and the con- 

 sequent continuous formation of sulphurous acid gas (SO2) which accounts 

 for the lengthened deterrent effect. 



Cattle Warbles. 



The Warble fly has not yet gained a footing in Australia. Animals 

 have at various times landed from England wdth warble maggots in their 

 skins, the latest occasions being in 1903 (]^Ielbourne), 1904 (Hobart) and 

 1908 (Sydney). During the period of detention in quarantine, however, the 

 maggots have been successfully destroyed and the continent thus saved from 

 the enormous financial losses which this parasite has been responsible for 

 in many other countries.^ 



This loss occurs mainlv through the depreciation in value of hides on 

 account of the perforations in them. 



In view of the possibility of the seaward guard, which up to the 

 present has been effective, being evaded a short description of cattle 

 warbles is here introduced. 



The fly belongs to the same family as the horse bot fly and is called 

 (Estrus or Hyfoderma bovis. It is somewhat like a bumble bee in 



' The annual monetary loss in the United Kingrdom i<i recorded by Fleminu; in Neumann's " Parasites 

 of Domesticated Anim als" as rangine: from seven to ei'^ht millions stei'ling-. 



