The Sheep Blow-Fly in South Africa. 449 



THE SHEEP BLOW-FLY IN SOUTH AFRICA. 



II. 



II. I\. ^frMiM), H.Sc, IMvS., Division of I\iiloiiiolog-y. 



Invkstigatjoxs undeitaJveii in regard to the pi'evalence and distribu- 

 tion of blovv-fiies in South Africa have shown that three species at 

 least are concerned in blowing sheep's wool. Nothing definite has 

 hitherto been done Avith regard to this pest in South Africa, and only 

 a few scattered references to its presence can be found; these indicate 

 that l)low-flies have only been noticed as a pest of sheep within the 

 I)ast twenty years. Lately the suliject has also been taken up by 

 Mr. J. W. Shoebotham, of the Cooper Technical Bureau at Iloodekoi) 

 in the Transvaal, and he has published some notes in tlie Farmer'fi 

 Weekly. Practically all that is known of these Hies is from the 

 results of investigations carried out in Australia. lirieliy, the general 

 liabits of these flies are as follows: JNormally they breed in carrion, 

 hut have developed a hahil of depositing their progeny on the wool 

 of sheep, especially round the hindquarters, and wliere the wool is 

 soiled. The maggots usually work into the sidn, sores are formed, 

 and the Avool drops off; finally the sheep dies of septic poisoning. 



The three species incriminated in South Africa are Fycnosoina 

 chloropyga, Wied., Fycnosoina alhiceps, Wied., and Lucilia seticata, 

 Meig. ; their relative abundance in the various parts of the Union has 

 not 3^et been fully ascertained. The two species of Fycnosoma are 

 widely spread over Africa and Asia, and tlie Lucilia is a common 

 blow-fly in other countries. 



No definite statement can be made as to why these flies should 

 take to blowing the wool of sheep, but there may be something in 

 the assumption that they have a natural tendency to change theii' 

 pabulum from dead to living meat. Some evidence of this is perhaps 

 given by the fact that one species at least has permanently taken 

 up a parasitic in preference to a saprophytic mode of life. Wool 

 presumably becomes attractive to the Hies when soiled with urine, 

 pus, or blood, but the following observation may be interesting in 

 this connection. The tAvo species of Fycnosoma have so far only been 

 bred from wool in the coastal region, that is Avithin a hundred miles 

 or so from the coast; but Avithin this region there appear to be tAvo 

 sub-regions, in the one of which, that portion Avithin ten miles of 

 the sea, the flies are liardl}^ active at all in bloAving avooI. This Avas 

 Avell seen in a lot of some six hundred sheep on a coast farm ; none 

 of these were infested Avith nuiggots, although they had not been 

 crutched, and the avooI round the hindquarters Avas Avhat one might 

 call normally Avet Avith urine. The interesting point is that, as the 

 owner told the Avriter, if these sheep were taken up to a farm some 

 sixty miles inland, they Avould become l)lo\vn very soon. Tlie only 



