SPECIES OF THE GENUS MUSCA, LINNAEUS. 413 



which may feed side by side with it. For these reasons, then, I consider it is important 

 to determine the true identit3/ of this tropical house-fly. But in order to settle this 

 question beyond any further doubt, it will be necessary to examine and compare 

 the external genitalia of both sexes Mdth that of Musca domesiica, and to do this a 

 large number of specimens from many parts of the world will be required, and this 

 is one of the reasons I have raised this point, in the hope that this material will be 

 collected. I have already begun the study of the external genitalia of the Indian 

 species in order to compare it with that of domestica. 



But the genus Musca contains another important group of species which have a 

 direct bearing on the health of valuable stock animals, and which have in the past 

 been confused with Musca domestica. The species I refer to, largely if not entirely, 

 feed on blood and serous and pustular discharges, and are exclusively outdoor insects. 

 Anyone who has watched a milch cow being tormented by hundreds of specimens 

 of Musca autumnalis can hardly doubt that, apart from the possibihty of their 

 carrj'ing disease germs, they must reduce the milk-producing capacity of the 

 animal simply through wearing it out, as it constantly tries to drive them awa^'. 

 That flies do in this way so worry a cow as very materially to reduce the quantity 

 of milk it produces, has been proved beyond any doubt by observers in America. 

 These species of Musca regularly follow the true biting flies, sucking up any 

 remains of blood that exudes when the latter withdraw their proboscides. They also 

 regularly feed on the' discharge from sores, cuts, eyes and the nose. We kno\\' 

 nothing of the germ-carrying capacity of these species, and until all have been 

 systematically studied, and veterinary officers and others are able to recognise them, 

 we never shall. 



During the last 15 years I have almost continuously studied all the stages of 

 many of the species of this genus, and observed their habits in the field, for I am a 

 strong believer in combining sj/^stematic studies with field observations. I have 

 no doubt whatever that such field work gives one a much truer picture of the individual 

 species than mere microscopic study of the dried insect. Field observations, in 

 conjunction with studies of the breeding habits and the larvae, as well as microscopic 

 studies of the adults, are the only means that I know of for coming to a final conclusion 

 regarding some of the species of this genus. But as an isolated observer in the 

 tropics, without access to the scattered literature on the subject, I have been severely 

 handicapped in my systematic studies of the species. I have in the first instance 

 had to depend on others for determinations of the species, and also on the inaccurate 

 references to them in the general literature of the subject. As a result many errors 

 have crept into my papers, and for the benefit of those who may use them I will 

 draw attention to them in these notes. 



Recentty I had the first opportunity of studying the specimens in the National 

 Collection at the British Museum, comparing them with the Indian species, stud3'ing 

 many types, and lasth^ of consulting the complete literature on the subject. And 

 I would like to take this opportunity of thanking Major E. E. Austen, D.S.O., for 

 all the facilities and help he gave me. I have no hesitation in saying that were it 

 not for his extensive knowledge of the subject, which he freely placed at my disposal, 

 I could never have done as much as I was able to in the short time available. 

 My own collection, together with the splendidly arranged and rich National Collection, 

 has enabled me to unravel almost all the important synonymy. I have critically 

 examined all Walker's types, as well as Bigot's, which Mr. Collin kindly lent me 

 for the purpose, and for which I wish to take this opportunity of thanking him. 

 Although I fully realise that much has yet to be worked out before it will be possil^le 

 to be certain of the true identity of some of the species of the older writers, I consider 

 that my study of this extensive material is sufficiently important to call for immediate 

 publication. 



(5296) 2 H 2 



