Abstract
During the summer and fall of 1941, 19 samples of flies were collected in epidemic areas both during and after epidemics of poliomyelitis. Of 8 samples collected for the most part during the latter part of a local epidemic but within 10 days of the onset of a local case of poliomyelitis, 4 yielded the virus; whereas of 8 samples collected more than 10 days from the onset of the last local case, none yielded the virus. In 4 instances there was a potential (though not proven) source of virus (in the form of "exposed" human feces of recent origin) within a few yards or few feet of the site where fly collections were made. Collections of flies from 3 of these sites yielded the virus. No attempt is made in this paper to develop epidemiological implications from this finding.