THE BroLtocy or KPHYDRA SUBOPACA LOEW 607 
in the water of comparatively low salinity, and the writer has occasionally 
found a few water mites in such water. But with an overwhelming number 
and an elastic adaptability to various conditions in pools, Ephydra has 
so far outstripped its coinhabitants in competition that the principal 
place in this kind of habitat must be assigned to this species. 
HIBERNATION 
The larvae which do not pupate in late autumn live through the winter. 
They usually stay at the bottom of the pools and very seldom are found 
suspended between the surface and the bottom, asin summer. They are 
motionless and are covered with mud through the accumulation of sedi- 
ment. It is hard to distinguish them by looking over the surface of the 
pools; but in the overflowed areas, where the water is hardly more than 
three inches deep, a large number of them may be found lying on the 
muddy bottom. Sometimes, when the heat of bright winter sunshine 
raises the temperature, a few larvae may be seen crawling slowly. They 
will not pupate in cold weather but will wait until spring. 
The pupae of late autumn will remain undeveloped through the winter. 
Late in the season large numbers of pupae may be found. In the early 
spring of the next year pupae are always found before any other stage 
appears. From these emerge the first adults of the coming season. 
Adults are rarely found in winter. On a warm and sunshiny morning 
one or two may appear, feebly drifting around on water. It is believed 
that they hide themselves in crevices in the gravelly bank and in the 
loose soil around the pools in order to winter over. 
Hibernation in the egg stage, if it occurs at all, must be very exceptional. 
According to observations made in the laboratory, the females do not 
oviposit late in the season, even though the room temperature may be 
comparatively high. Eggs laid in the early fall remained undeveloped 
for a long period, and some of them died before winter commenced. Thus 
there is evidently very little chance for them to hibernate in this stage. 
SUMMARY 
1. Ephydra subopaca has a salt habitat. It is found in the salt pools 
at Ithaca, the density of which ranges from 1.5 to 7+ in August and 
from 4 to 11 in September, and the salinity of which varies from 1.76 to 
