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 27 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 qnadrisetosa, 
Sepsis violacea, Nemopoda minuta, Limosina albipen- 
nis, Limosina fontinalis, SpJueroccra snbsultans, and 
Scatophaga furcata, while the most abundant forms 
captured on excrement were Phorbia terrcenovce and 
Borborus equinus. It will also be noticed that among 
the reared forms there are ten others which are simply 
