Ee 
(Sean) 
XVII. The Vinegar-fly (Drosophila funebris). By ERNEST 
Ewarr Unwin, M.Sc. Communicated by Pro- 
fessor L. C. Mraz, F.R.S. 
[Read March 20th, 1907.] 
VINEGAR-FLIES, small brownish two-winged flies with 
bright red eyes, belong to the Muscid family. The 
commonest species is Drosophila funebrrs. 
Drosophila larve live in rotten and fermenting fruit ; 
they also frequent beer and vinegar casks. Dufour * men- 
tions finding them in marmalade, and between the layers 
of a decaying onion, and other records give mincemeat 
and poor butter as places where the larve have been 
found. Howard + includes Drosophila among the common 
excrement breeders. I have found the flies feeding on 
putrefying mussels, and an open decanter of claret will 
attract swarms of them in the summer time. The larve 
of another species have been found mining the leaf-stalks 
of swedes (see below). Slices of tomato, squashed plums 
or other fruit readily attracted the flies to the laboratory, 
and a large supply of all the stages was easy to obtain for 
examination. The flies are most abundant during the 
summer months, but in the laboratory they persist well 
into the winter, and eggs have been laid as late as the 
end of November. 
Outline of Life-history.—The fertilised female lays her 
eggs in the fruit-pulp, and after three days or so 
small whitish maggots can be seen crawling about the 
mass. These feed continually, grow rapidly, and become 
full grown in about three weeks. They then leave the 
pulp to find a convenient place for pupation. The natural 
place is the soil, but they readily pupate on the sides of 
vessels, or even upon a dryer portion of the pulp. The 
last larval skin is retained as a puparium, which turns 
brown and hard. The duration of pupation, as well as 
that of the other stages, varies at different seasons of the 
year; in summer it may be as short as a week, or it may 
* Dufour (1839 and 1845, 2). + Howard (1900). 
TRANS. ENT. SOC. LOND. 1907.—PART I. (SEPT.) 
