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A SURVEY OF THE AUSTRALIAN SHEEP MAGGOT-FLY PROBLEM. 



By T. Harvey Johnston, M.A., D.Sc, Professor of Zoology, 

 University of Adelaide. 



[Read August 9, 1923.] 



Though a sheep blowfly problem occurs in Great Britain. South Africa, 

 New Zealand, and some of the Pacific Islands, it is in the eastern half of 

 Australia that it has developed more especially. In North America there is a 

 myiasis affecting stock, caused by the screw worm, Compsornyia macellaria, but 

 it is of a c|uite different type from that occurring in the countries mentioned. 

 At least forty years ago certain blowflies were known to deposit their eggs or 

 larvae in injuries on ram's heads (caused by fighting), on blankets, saddle 

 cloths, and wool bales, but it was not till about 1896 that infestation of lambs 

 was noticed. The latter occurred after marking and tailing. Following the 

 drought years 1900 to 1902, fly infestation became more and more pronounced, 

 Froggatt referring to the matter early in 1905, again in 1910, and frequently 

 since then. In Queensland the invasion became so bad that in 1913 Cory and 

 Jarvis were commissioned to inquire into the matter and found that out of over 

 one million sheep in a district in Central Queensland an average of 23 per cent, 

 had been "struck," and that on some "stations" from 40 per cent, to 70 per cent, 

 of the animals were affected. They recommended that experiments with various 

 traps, dip fluids, and dressings should be carried out by the Government, this 

 being begun in 1914 and continued for four years at Gindie, near Emerald, 

 Centrjal Queensland (R. S. C, 1922, p. 45). 



A very good account of the damage done to sheep and wool, and the com- 

 moner sites of infestation, has been published by Froggatt (1913, p. 16; 1915, 

 pp. 12, 13). In the preceding paragraph an indication of the seriousness of the 

 infestation in Central Queensland is given. Froggatt and Froggatt (1916. pp. 

 28-30) published a return of the total sheep and estimated losses from blowfly 

 infestation in New South Wales for the year 1914, from information forwarded 

 by the district stock inspectors. It showed that the amount varied in different 

 districts from nil to as much as 8 per cent., the total estimated loss for the State 

 during the period being about 13 per cent. Russell (Editor, 1921, p. 250) stated 

 that the losses in 1920 from fly attacks in two Queensland "stations" were 

 estimated at about 15,000 sheep in each case, all the sheep being almost fully 

 fleeced. The writer was informed in 1920 by Messrs. Russell (of Dalmally, 

 Roma) and W. G. Brown (Sheep and Wool Expert, Dept. of Agriculture, 

 Queensland) that the losses from fly probably averaged 5 per cent, of Queensland 

 flocks — a loss as great as that from all natural causes combined (old age, lambing, 

 accidents, and disease). The loss is even greater in New South Wales, where 

 sheep raising is carried on more extensively. Fly infestation also occurs, but 

 to a less extent, in Victoria, Tasmania, South Australia, and Western Australia. 

 The annual loss, both directly and indirectly, must aggregate some millions of 

 pounds sterling. McLeod and Holme (in Cooper, 1913, p. 55) estimated the 

 direct damage in New South Wales during the season 1909-1910 at i377,700, 

 and mentioned that in one station in that State fully 60 per cent, of the sheep 

 shorn in March became attacked, and, as a consequence, a later date was fixed 

 for subsequent shearings with improved results. 



In the Sydney Morning Herald of December 28, 1921, it was stated that 

 the destruction of sheep and lambs, the reduction in wool, and other losses 



