HIPPOBOSCA STRUTHIONIS. 59 



means of checking their increase. They do not lay eggs ; 

 neither, as is the case with some flies, produce living 

 maggots, but the maggot lives and feeds inside the 

 abdomen of the female fly until it is full grown ; then it 

 forms a kind of roundish, white or yellowish, case, which 

 is deposited by the fly, and in this case the maggot 

 changes to the pupa or chrysalis state, from which the 

 fly presently comes out. How soon this happens would 

 be useful to know, and might easily be found out by 

 putting some of the cases in a box in tolerably natural 

 temperature and watching for appearance. 



The cases sent me were much like little roundish 

 white balls, with a brown spot on one side : it is very 

 likely that they would be found shortly to turn, like 

 those of the European Hippobosca examined, found on 

 horses and cattle, to a black colour. 



As Mr. C a wood mentions that he did not find any of 

 these cases on the infested ostriches, and it is quite 

 plain that it was laying time with the flies, for I saw 

 cases they had laid, with them in the bottle, it may 

 fairly be presumed that a large proportion of them fall 

 to the ground ; and here we get to what might be a 

 measure of prevention. 



If the ostriches remain on the ground where the fly- 

 cases have fallen, it is almost certain when the flies come 

 out of the cases that they will start a new attack ; but 

 if ground could be changed so that a dressing of quick- 

 lime, or anything that would kill the contents of the 

 cases, could be run over the ground, and the birds 

 individually dressed so as to remove at least a good 

 proportion of the flies, so that they should not infest the 

 new ground, this would appear likely to lessen the 

 amount of attack greatly. 



If any poultry can safely be allowed to run on ostrich 

 fields or folds, these might probably be turned to good 

 account in picking up the egg-like fly- cases which drop 

 from amongst the ostrich feathers, especially when the 

 cases are still white. 



The European kind of fly (Hippobosca equina) usually 



