APPENDIX II 
On Some Flies Reared from Cow Manure* 
I N the summer of 1889, while engaged in an investi¬ 
gation of the habits and life history of the horn fly 
of cattle (Hceniatobia serrata), the writer at various 
times brought to Washington, from different points 
in Virginia, large quantities of cow manure collected 
in the field, and eventually succeeded in working out 
the complete life history of the horn fly, as displayed 
in Insect Life, Vol. II, No. 4, October, 1889. In this 
article the statement is made, in concluding, that the 
observations were greatly hindered and rendered dif¬ 
ficult by the fact that fresh cow dung is the nidus for 
a number of species of Diptera, some about the same 
size and general appearance as the horn fly, and that 
no less than twenty distinct species of flies had been 
reared from horse and cow dung, mainly the latter, 
and six species of parasitic insects as well. The plan 
finally adopted of securing the isolation of the horn 
flies was to remove the eggs from the surface of the 
dung and place them with dung which was absolutely 
fresh and collected practically as it fell from the cow. 
A report upon the other species was promised, but was 
never published, although Professor Riley, in his re- 
*Reprinted from an article with this title, by L. O. Howard, 
published in the Canadian Entomologist, Vol. 33 (1901), pp. 42-44. 
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