44 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
iy to the sides of the bottle that even thoro washing at the dairy fails to 
remove them. When the bottles are filled, the insects stand out so 
prominently that they are usually noted by the inspector and discarded, 
but an occasional one gets to the wagons and is delivered to a customer. 
There can be no doubt that in a properly managed dairy the pupae 
are not only killed but are rendered thoroly innocuous. The bottles are 
treated witha hot, almost boiling, caustic solution, washed in hot water 
and come through the washing machine so hot that they cannot be han- 
dled with comfort. In this condition there is nothing about them to at- 
tract flies and the further process of bottling and sealing affords no op- 
portunity or inducement for ovipositing. Even if eggs could be in- 
troduced at this stage the milk would be disposed of before there was 
any opportunity for the development of the later stages of the insect. 
In view of the known habits of the pomace flies there is no reason 
to suppose that the forms attracted to sour milk would necessarily be 
of one species. Ina cream bottle secured subsequent to the inspection 
trip there occurred along with the above described species a preponder- 
ance of a considerably larger type of puparium. These measured 5 mm. 
in length, nearly twice that of the other species, and were of a bright 
brown color. The caudal spiracles were borne on paired tubercles. 
In spite of an extensive search I failed to find in the entomological 
literature any mention of Drosophila breeding in milk. The nearest 
approach is an untraced reference to their occurring in rancid butter. 
However, the phenomenon has not completely escaped attention. In the 
Zeitschrift fur Fleisch und Milchhygiene, 1913, Vol. XXIII, p. 252-253, 
Otto Fettick reports a similar case which came to his attention. The 
specimens were in bottled milk which had been obtained from a large 
distributing station. ‘Tho it is obvious from his description that he 
was likewise dealing with puparia, he regarded them as larvae of 
Drosophila or a related genus. He was unable to breed the adults and 
concluded that since no motion was to be detected in the “larvae” they 
were dead when received. 
Fettick speculates as to the source of the contamination and dwells 
especially upon the sanitary aspects of the question. He says: 
“Fly larvae of this genus find suitable conditions for living in 
shallow, easily warmed, foul water, containing organic matter, as well 
as in moist, fermenting substances. They cannot live in pure spring 
water suitable for drinking, or in tap water, into which, moreover, they 
cannot get on account of their size (! R.). It is, therefore, highly 
probable that the larvae found in milk reached it at the producing sta- 
tion probably through washing and rinsing of the cans or milk 
