The Sheep Blow-Fly in South Africa. 455 



its margin is entire; tlie "button" is situated un the peiitreme, 

 and has a small rounded opening in its centre. The three straight 

 slits are very similar to those in the other two species, but are rather 

 narrower. 



The eggs are laid in batches from half a dozen to fifty and 

 more, and the young maggots hatch in twenty-four hours, becoming 

 full grown in five days. An interesting habit of these maggots has 

 been observed in the breeding jars. When full-grown they do not 

 burrow down into the soil, but congregate on the soil just underneath 

 tiie piece of meat in which they have been feeding. They become 

 pinkish in colour, and reniain passive in the fully extended larval 

 ccjiidition for two or three days, when they contract, and then pupate. 

 Adult flies emerge in four or five days. The foregoing details refer, 

 of course, to conditions in n)idsummer; cooler weather lengthens 

 the life-histoiy. 



The Grey Flesh-fly. 

 Sarcophaga haeuionhoidalis, Fall. 



Although this fly has not been found to blow wool, it is 

 mentioned here, as it is one of the flies that most commonly blow 

 meat. It is common everywhere, but appears to be much more 

 frecj^uent in towns than in the country. It proved itself a great 

 nuisance in experimental work, as its maggots were sure to become 

 present in every piece of meat exposed unless special precautions 

 were taken to prevent them gaining access to it. The young* maggots, 

 which are extruded alive by the parent fly, can travel quite a good 

 distance in order to reach their food, so that even when one cage was 

 placed within another tliej" Avere not alwaj's kept out. However, the 

 full-grown maggot is easily recognized once it is known. It is large, 

 robust, and somew^hat flattened dorso-ventrally ; a conspicuous feature 

 is that the area on which the posterior stigmata are situated is deeply 

 sunken, its upper and lower borders forming very distinct lips, 

 which, when the maggot is still alive, are continually closing and 

 then opening suddenly. The stigmata are in the upper part of 

 the area, and perhaps in co-relation with the extra protection afforded 

 by being in a cavity they are very slightly chitinized. The peritreme 

 is very slight and has a very wide opening; the slits, too, are slight 

 and narrow. 



The adult fly will easily be recognized as the common large 

 grey fly, which has a distinct chec[uered pattern on the abdomen. 



Material for Stuijy. 



During the course of this paper reference has been made to the 

 fact that much still remains to be done before it can be said that 

 everything is known about the sheep blow-fly in this country. So 

 far three species have been found troublesome in sheep, but it is 

 cjuite possible there may be others. There are questions relating to 

 the abundance and distribution of those that are known; also to their 

 seasonal distribution and the effects of di'ought and of wet seasons 

 on the numbers of the flies. Parasites may be present, and perhaps 

 one only needs to be discovered and encouraged for it to^ become an 

 efficient help in combating the blow-fly pest. 



