The Sheep 13lo\v-F]A" in South Africa. 453 



Full details of the life-history of this species have not yet been 

 worked out, but in J*]ast London, during- December, the whole develop- 

 ment took place in about ten days. Some attempt has been made to 

 determine the number of eggs laid by each female, but for various 

 reasons the flies in the experiments all died before anything could 

 be done; however, from dissections it would appear that the ova 

 are not fully developeil when the female fly first emerges from the 

 puparium, and some days must elapse before she is ready to oviposit. 

 There is therefore quite sufficient time for the flies to be killed by 

 means of poisoned bait; the adult flies must have food, and in the 

 laboratory they took readily to honey soon after they had emerged. 

 In bright sunshiny weatlier the flies can be seen sucking nectar from 

 flowers in gardens and in the veld. Individual flies live quite a 

 considerable time, and it is even possible that some are able to 

 survive the winter, as the writer has often found them indoors during 

 winter in Pretoria. 



The Baxued Blow-fly. 

 I'ljcnosouui aU)iceps, Wied. 



This fly is very much the same size and shape as Pijcnusuma 

 cliloiopyga, but looks very different. It is a bright shining green, 

 and appears to be banded owing to the presence of narrow, darker, 

 blackish bands at the edges of the segments and across the thorax. 

 It ranges as widely as P. cJiIoropyrja, but recent observations would 

 indicate it has a diifeient seasonal abundance. In the early part 

 of summer, that is about October and November, P. alhiceps formed 

 about 10 per cent, of the flies reared from dead sheep, and was not 

 found at all in wool at that time. Later, however, towards the end 

 of January, it was found infesting wool to the extent of about 50 

 per cent, or more, and in a dead sheep this species preponderated to 

 the extent of 90 ])er cent. It is interesting to note that in the 

 infested wool the maggots of P. alhiceps were all quite young, while 

 those of /-'. rlihnopjuja weie full grown, which would seem to indicate 

 that the laiiei- is the one primarily lesponsible for blowing sheep, 

 but it still remains to be proved wheiJier this is always the case. 



The maggot of this si)ecies can be readily distinguished; it is 

 not smooth and while, l)ut tlie whole surface of the body is covered 

 with rows of protuberances or i)apilhie, at the eiuls of which are 

 set tufts of short spines. There are fourteen of these rows, and those 

 on the upper surface are much larger and darker than those on 

 the lower surface. The upper surface, too, is much darker than the 

 lower, the darkening being due both to pigmentation of the skin, 

 and to the presence of a number of dark, rough, raised spots aggre- 

 gated in patches in the centre of each segnient. This maggot has 

 another peculiarity; when it is touched it plays " possum," holding 

 the body rigid in a curved position. The posterior stigmata (Fig. 3) 

 are quite distinctive, although iji this case not so necessary for 

 purposes of identification. The area on which they are situated is 

 surrounded by tubercles similar to those on the rest of the body, 

 only here they are much larger, while the tufts of spines on them 

 are smaller. The stigmata are even more heavily chitinized than 

 in the case in the maggot of P. chloropyga, the peritreme is very 



