DROSOPHILA GIN BOTTER DS CERTIFIED) MibK 
By Wo. A. RILEY 
The finding of conspicuous extraneous matter in the household 
milk supply is never very appetizing. When such material is found in 
certified mill in bottles bearing the label, “This milk is certified by your 
State Board of Health,” the customer is quite likely to feel and to 
express an especial resentment. An instance of this nature which 
recently came to my attention proved of much entomological interest 
and led to a study which revealed that such cases are not so rare as 
might be suspected from the fact that they do not seem to have been 
recorded in our literature. 
Early in September there was submitted to me a quart bottle of 
milk which bore scattered along the sides some thirty small seed-like 
specks about 214 mm. in length. Altho these were minute, they stood 
out very conspicuously against the white background of the milk, as is 
evident from the photograph reproduced herewith. In general appear- 
ance they resemble grass—or “hay”’ 
seed and are often so interpreted 
by workers in the dairies and distributing stations. More detailed ex- 
amination revealed that the “seeds” were the puparia of a fly of the 
genus Drosophila. Attempts to secure adults were made, but for 
reasons which will appear later, these were unsuccessful. 
The puparium does not correspond to any of the few that have 
been accurately described. It is hoped that the accompanying figure 
and the following notes may serve to definitely identify the species 
when more is known concerning the life histories of the group. 
The puparium is of a light straw color, 21% to 3 mm. in length by 
0.8 mm. in width, strongly convex on the dorsal surface, but slightly 
so on the ventral surface. The segmental limits and the cuticular ap- 
pendages are well shown in the figure. The pharyngeal skeleton of the 
larva is retained as a conspicuous black mass near the anterior end of 
the puparium. The dorso-cephalic region is flattened: and from it 
project the two digitate pupal spiracles. The basal portion of these 
processes measures some 200 microns in length by 50 microns in diam- 
eter and bears 11 filiform processes measuring up to 300 microns in 
length. oe 
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1Published with the approval of the Director as Paper No. 145, of the Journal 
Series of the Minnesota Agricultural Experiment Station. 
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