208 



must be had to the (hp ; the dip also being necessary to exterminate other external 

 ])ara.sites. So far there have been no losses from arsenical poisoning. When 

 the sheep are dipj)e(l they should not be overheated; not dijjped after midday 

 in winter, and not after 4 p.m. in summer. 'I'hey should not be driven immedi- 

 ately after dip[)ing. .Strict allcnlion to these important i)oints means that losses 

 are practically nil" (J\. S. C"., 1922). 'Jhere is no need to crutch after these 

 various niethods of treatment. 



'lliese results, based on experiments with thousands of sheep, must carry 

 weight, i.ii spite of the fact that they are opposed to the statements of the New- 

 South Wales investigators. Froggatt and ]M-oggatt reported against the frequent 

 spraying and dipping of sheep with arsenical solution of excessive strength on 

 account of the danger of arsenical poisoning, and stated that though a spray 

 containing 1^- lb. arsenitc of soda in 16 gallons of water maybe used as a surface 

 application, not more than l^ lb. in 50 gallons of water should be used if intended 

 lo reach the skin (1917, p. 20). The latter would mean only 03 per cent, 

 arsenitc of soda and a much lower percentage of arsenic. In a later article 

 ( 1918, p! 14) they recommended the former strength (i.e., nearly 1 jjer cent, 

 arsenitc solution) for use when jetting, and mentioned that about three weeks 

 was the longest period for which the best proprietary specific retained any pro- 

 tective value. A little later, iM-oggatt (1922, pp. 14, 19) stated that jetting (at 

 Warrah, New South Wales) at a pressure of about 125 lbs. cost one half -penny 

 per sheep, the soluticjn containing 1 lb. arsenic in 40 gallons water (i.e., 25 per 

 cent, arsenic). 



. Mr. iM-oggatt's contentions were traversed in the Brisbane Press (1922) by 

 Messrs. Russell and W. G. Rrown, who reiterated the results reported above 

 relating to experimental work at Dalmally. 



The writer would like to suggest that the arsenical treatment, by whatever 

 method,' may owe its efiicacy as a protection against fly to the fact that the 

 poison destroys the bacteria present in the soiled or damp wool or in the sores, 

 and thus may render such treated parts quite unfavourable as sources of food 

 sui)ply for any larvae which may be deposited. Besides, the fact that the 

 putrefactive and other organisms are killed, causes a cessation in the ])roduction 

 of those odours which have a chemotropic influence on the female blowfly — thus 

 not only is the attractive influence more or less destroyed for the time being, 

 but also any eggs or larvae which may reach such wool, encounter a powerful 

 contact poison, and, besides, are in a material in which the organisms that 

 appear to be necessary to produce conditions favourable to the fly larvae, have 

 been more or less destroyed, so that starvation may result. 



It is known that some insects, including flies, are attracted to certain plants, 

 and it was suggested that members of the genus Sfapclia (natives of South 

 Africa) might be grown in expectation that blowflies would be misled by the 

 carrion-iike odour of the flowers of such plants and deposit eggs on them, such 

 eggs or larvae resulting from them perishing, b'roggatt (1915, p. 42) com- 

 municated with the South African entomologist who reported adversely and 

 pointed out that South Africa enjoyed no special innnunity from blowfly, though 

 Stapelias were native plants there. 



In.the Kew Bulletin (No. 10, 1922; Nature, I'ebruary 10. 1922) Stapf 

 reported that a Brazilian "stink grass" (Mclinis ininulijlora i)icniiis) possessed 

 an oil with insect-repelling c|ualities, and thought it might be introduced into the 

 tsetse-fly belt in Africa to act as a food for cattle and as a fly repellent. He 

 referred to its attempted introduction into .Xustrali^a (Kew Bulletin, 1900), but 

 no furlher information was available regarding it there. The writer is not 

 aware of [\\v plan! ha\'ing been utilized against blowfly in the ( "ommonwealth. 



