278 THE HOUSE FLY— DISEASE CARRIER 



other conditions. Thus some of the species here indi- 

 cated as scarce in connection with excrement may be 

 very common under other conditions, which would 

 indicate that their occurrence upon excrement was more 

 or less accidental. Moreover, certain of the species 

 which have been captured on excrement, but not reared 

 •from it, are nevertheless undoubtedly excrement breed- 

 ers, as will be proved by future observations. Thus 

 we have in several cases certain species which have been 

 reared while congeneric species have simply been cap- 

 tured, as, for example, Nos. 7 and 8 of the captured 

 species are congeneric with 7, 8 and 9 of the reared 

 series; 11 and 12 of the captured series are congeneric 

 with 13 of the reared series; 17 of the captured series 

 is congeneric with 18 of the reared series; 22 and 23 

 of the captured series are congeneric with 27 of the 

 reared series; 25, 26 and 2^ of the captured series are 

 congeneric with 28 of the reared series ; 33 of the cap- 

 tured series is congeneric with 32 and 33 of the reared 

 series, and is undoubtedly an excrement breeder, and 

 the same may be said of 36 of the captured series which 

 is congeneric with 36 of the reared. 



From these data it will be noticed that the most 

 abundant species reared were Helicobia qiiadrisetosa, 

 Sepsis violacea, Nemopoda minuta, Limosina albipen- 

 nis, Limosina fontinalis, Sph^eroccra suhsultans, and 

 Scatophaga furcata, while the most abundant forms 

 captured on excrement were Phorbia terrccnovcc and 

 Borborus equinus. It will also be noticed that among 

 the reared forms there are ten others which are simply 



