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, f r 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 terr&novcc 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 fly, and some of them are sometimes found 

 in houses. The common widespread flesh fly of Europe 



