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- 
