254 > THE HOUSE FLY—DISEASE CARRIER 
from twenty-two to twenty-three days. This blow fly 
is a characteristically out-of-door fly, but under cer¬ 
tain circumstances may be found in houses in some 
numbers. In October, 1899, for example, a gentleman 
living in the suburbs of Washington found thousands 
of these flies in his cellar. No cows or horses were 
kept near the house, and there had been no dead ani¬ 
mals about so far as he knew. It is probable, however, 
that these flies had come from some dead animal, and 
had sought the cellar for hibernating purposes, al¬ 
though the weather was still warm. 
Phormia terrcenovce Desv. (Fig. 30.) The bluebot¬ 
tle fly just mentioned is a rather large species. The 
Phormia, however, is a medium-sized or rather small 
bluebottle. It was originally described from New¬ 
foundland, but is widespread in the United States. It 
is occasionally found in houses, and I have more than 
once seen them upon window panes. It is abundantly 
attracted to human excreta, and has been taken under 
many varying conditions about Washington: enormous 
numbers were found on one occasion in the sinks of a 
deserted militia camp at Leesburg, Virginia. 
The Flesh Flies (Sarcophaga assidna Walk.) 
We include under this heading the flies of the genus 
Sarcophaga, on account of the significance of the sci¬ 
entific name, although many Sarcophagids are not true 
flesh eaters. Several of them very closely resemble 
the house flv, and some of them are sometimes found 
in houses. The common widespread flesh fly of Europe 
