310 The Philippine Journal of Science 1923 



Region, and the present collection clearly shows this to be the 

 case. 



As I have now studied nearly all the existing types of the 

 genus Musca, I am in a position to give the species their correct 

 and final names, as well as all the synonyms. In studying any 

 large collection of species of this genus it is not only convenient 

 but also most satisfactory to deal with them in three groups, 

 into which they naturally fall as follows : 



The nonbiting, occasionally hsematophagous, true house- and 

 bazaar-frequenting species, which, though often found on 

 animals, are mainly associated with man, his dwellings, and his 

 food. They breed in garbage and excrement of all kinds and 

 regularly feed on these. It is hardly necessary to point out 

 that the species of this group are some of man's most-dangerous 

 insect pests; but, unfortunately, we are not able to gauge with 

 any degree of accuracy the amount of harm they do. Although 

 no one has yet succeeded in isolating known species of patho- 

 genic bacteria from wild specimens (that is, flies caught in 

 houses and bazaars), practical experience has taught us to regard 

 them as certain carriers of pathogenic bacteria, helminth eggs, 

 and parasitic protozoa from excrement to the human body and 

 to food of all kinds. More than one species is the invertebrate 

 host of species of Habronema parasitic in horses and cattle. 



The nonbiting, haematophagous species comprising this group 

 are only found on animals and in their vicinity, and breed al- 

 most exclusively in cow dung. There is very little doubt that 

 the species of this group are mechanical carriers of blood para- 

 sites and bacteria from one animal to another. Anyone who has 

 observed their habits in the field will be in a position to ap- 

 preciate their potentialities in this direction. Representatives 

 of this group are to be found in most parts of the world feeding 

 on cuts, abrasions, wounds, sores, and the discharge from the 

 eyes of animals as well as on the blood and serum which exude 

 from the bites of true biting flies. Owing to the nature of their 

 food, these species are essentially intermittent feeders and may 

 be seen flitting from one animal to another in search of food. 

 But here again Mitzmain has shown that some of them are 

 certainly under suspicion as carriers of pathogenic trypano- 

 somes, but there is at present no experimental proof that they 



