42 
the whole number of flies captured in kitchens and dining rooms, and 
while it was by no means one of the species most commonly captured 
upon excrement, it was shown conclusively that under certain condi- 
tions this insect may be a factor of the greatest importance in the 
spread of intestinal disease. In the most cleanly and best cared for 
portions of a large city these conditions do not exist. The admirable 
water supply and sewerage systems pertinent to such localities—the 
admirable water-closet facilities which sanitary plumbing has carried 
to such a degree of excellence—obviate in a large measure typhoid- 
transfer possibilities, yet, even in such places, where the vessels used 
in the sick room are not promptly disinfected and where by reason of 
neighboring stables house flies are especially abundant (since these 
creatures breed by preference in horse manure), the possibility may 
still exist, but in army camps where feces are left exposed the house 
fly will and does breed in this substance in large numbers and in 
Fic. 21.—Drosophila ampelophila; a, adult; b, antenna of same; c, base of tibia and first tarsal joint of 
same; d, puparium, side view; ¢, puparium from above; f, full-grown larva; g, anal spiracles of 
same (author’s illustration). 
towns where the box-privy nuisance is still in existence (and this 
applies to very many farmers’ houses in the country) the house fly is 
a constant source of danger. Moreover, in the low quarters of a 
large city where there is lax sanitary supervision, in the open lots 
surrounded by an ignorant population, feeces are frequently deposited 
in the open, sometimes in close proximity to kitchens, and thus may 
become very dangerous. 
The other species of flies which are of especial importance are as 
follows: The little fruit flies of the genus Drosophila, and especially 
Drosophila ampelophila (fig. 21), which is so commonly found in 
houses in the autumn, attracted to overripe or partly decaying fruit, 
and which sometimes swarm in great numbers about the fruit stands in 
markets, isalso an excrement breeder, and at certain times of the year 
becomes an important form in the disease-transfer relations. The 
species known as the little house fly (//omalomyia canicularis and TZ. 
