42 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
At the posterior end is a pair of spiracles 
which represent the single ones of the larva 
in Drosophila ampelophila and D. amoena, 
whose life histories, thanks to the studies 
of Professor Comstock in 1882, are the best 
known. These spiracles are borne upon a 
pair of clearly separated tubercles. In the 
species under consideration, however, they 
are carried on the distal end of a single 
caudo-dorsal process, as is shown by the 
illustration. 
Naturally, both the customer and the 
milk distributing company were anxious to 
know the nature and the source of the in- 
festation, while the health authorities were 
interested in the possibilities of other gross, 
tho less conspicuous, contamination. In 
order to investigate conditions five of the 
large distributing companies of the city 
were visited. In each place I found that the 
occurrence of these peculiar) “seeds sven 
“bugs” was well known. All agreed that 
they were most commonly found earlier in 
the season tho two samples were obtained 
at the time (September 30) and at another 
lai are teytemaioes place they had been observed that day but 
discarded. Two more infested bottles were 
obtained the next day. Thus it would appear that the phenomenon is 
not a rare one. 
It developed, as was to be expected from the habits and length of 
the life cycle of the flies, that the contamination was in bottles which 
had been returned to the central stations infested. Lying about homes 
and especially about restaurants and saloons, they had served to attract 
the flies which oviposited in the souring milk. It was very significant 
that one proprietor noticed the difficulty most frequently in Bulgarian 
buttermilk bottles. That this was not the only source was evident 
from the fact that the difficulty was observed in dairies that did not deal 
in buttermilk, and that two of the samples sent were in cream bottles. 
Judging from known life histories, the hatching larvae from the 
first deposited eggs would be pupating within a week. The pupae are 
sufficiently transparent to escape careless inspection and adhere so tight- 
