ZOOLOGICAL POSITION 3 



rather uniform, except that with a few of them the 

 adults bite and suck blood, while the majority, like 

 Musca domestica, do not. The tsetse flies of Africa, 

 belonging to the genus Glossina, bite, as also do the 

 stable flies of the genus Stomoxys and the cattle flies 

 of the genus Hsematobia (this genus includes the so- 

 called horn fly of cattle). Of the other genera, Graph- 

 omyia, Morellia, Mesembrina, Pyrellia, Pseudopyrel- 

 lia, and Phormia all breed in excrementitious matter. 

 The genus Myospila, formerly placed in the Muscidse 

 but really anthomyid, is also a breeder in this material. 

 The flies of the genus Muscina breed in decaying vege- 

 tation and in cow dung, as also do those of the genus 

 Pollenia. Those of the genus Cynomyia and of the 

 genus Calliphora and of the genus Lucilia breed in 

 dead animal matter, while Chrysomyia macellaria — 

 the famous screw-worm fly — breeds in living flesh. 



Some of these flies are occasionally found in houses, 

 and further consideration of them will be found in 

 Chapter V. For practical purposes they are all equally 

 dangerous, as possible disease carriers, and to the prac- 

 tical person there is no especial need to distinguish 

 among them ; but fortunately the house fly is the only 

 one that comes in abundance to houses. It is the only 

 one which really deserves the term domestic. 



For the two following paragraphs, which indicate 

 the easiest method of distinguishing the house fly from 

 any of its allies, I am indebted to Mr. D. W. Coquil- 

 lett, an authority on the order Diptera : 



''From nearly all the other kinds of flies that resem- 



