THE BroLtocy or ErHyYDRA SUBOPACA LOEW 599 
number of pupae were kept in bell jars in a greenhouse where the tempera- 
ture registered 45° C. between 1 and 2 p.m. In this experiment all 
the pupae died at the end of the day. 
THE ADULT 
Emergence 
The transformation to the adult stage was observed in the laboratory. 
The fly came out by breaking off the oval disk of the dorsum at the anterior 
part of the puparium. It struggled at the opening of the pupal case, but 
finally emerged without much difficulty. Each of its legs wrinkled like 
a French curve, and its ptilinum bulged like a glass globe. The ptilinum, 
with its somewhat pubescent surface, expanded and contracted at short 
intervals for about thirty minutes. The ptilinum then sank into the 
head, leaving a transverse cavity in the front. The sinking was gradual, 
and the ptilinum was pushed out again several times, but each time the 
pushing was weaker. Finally the cavity at the front was gradually 
narrowed to a very thin cleft. The fly moved around on the water sur- 
face and frequently rubbed its abdomen with its hind legs. About a 
quarter of an hour later it began to rub the tips of its wings. Through 
constant rubbings the wings began to expand at their tips, until they 
became straightened and entirely spread. The fly then gave a few more 
strokes and was ready for flight. 
Food and feeding habits 
The alimentary canals of ten flies were dissected and examined. The 
contents consisted almost entirely of Chlamydomona and Navicula. 
Bacteria, Mastigophora, and inorganic materials were found only occa- 
sional’y. 
Ephydra subopaca feeds in the same manner as does the house fly, but 
resting on water, on the floating scums, on leaves and the like, in the pools 
or on the surface of soft mud. 
Preference for stagnant water 
A calm water surface is most favorable for flies. They do not fly any 
considerable distance, and never higher than a foot above the surface; 
