LIFE HISTORY OF HYDROUS ( HYDROPHILUS ) TRIANGULARIS. 
33 
where specimens of the same bass are often kept under experimentation. In every 
instance the larva was instantly seized and swallowed, sometimes almost before 
it struck the surface of the water. This indicates that not only do these fish eat 
the larvae when they can get them, but that the larvae ought to make successful 
bait when fishing. 
ENEMIES OF THE PUPAL. 
It might seem at first sight that 'the pupa was admirably protected by being 
buried in the moist earth, but even there it is subject to certain dangers. The first 
of these is from ants. Two pupae were unearthed in July that were half eaten up 
by small ants, which literally filled their pupal chambers. Of course, a larva 
when ready to pupate will seldom choose an ants’ nest in which to form its pupal 
chamber, and it will not often happen that ants drive one of their galleries into a 
pupal chamber after it is formed; but the finding of these two half-eaten pupse 
shows that this does happen occasionally, and the larger the number of ants along 
the shores of a pond the greater are the chances of its occurrence. 
Another and much more serious danger for the pupa lies in a change in the 
moisture content of the earth in which the pupal chamber is built. If the amount 
of moisture in the soil is greatly changed in either direction, it is likely to prove fatal 
to the pupa. If it be raised excessively, then the chamber will be flooded and the 
pupa will be drowned. It is to guard against this very accident that the pupa skin 
is provided with the long curved spines described on page 24, while the pupa also 
arches its body strongly upward in order to lift the spiracles above any ordinary flood- 
ing. However, the pupal chamber is never far from the water’s edge, and any con- 
tinued rise in the water will flood it so completely that these safeguards will no longer 
avail. Two pupal chambers on the shore of pond 2, series E, were filled with water, 
and as a result the two pupse they contained were drowned within a few minutes. 
On the other hand, the soil that was moist enough when the larva began its 
pupal chamber may become baked and dried by the time the adult beetle is ready 
to emerge, and the latter may thus become imprisoned and unable to get out. The 
abrupt draining of this same -pond 2, series E, caught some beetles in just this way. 
As long as the water remained at its normal level the soil would have continued soft 
and moist; but when the water was entirely removed the hot sun soon dried and 
baked the mud so firmly that the adult beetles were caught and imprisoned in the 
pupal chamber. Two were found thus imprisoned on August 12. They were alive 
and vigorous and would possibly have remained so until released by the resoftening 
of the earth after the pond was filled again. Similarly, a piece of moist earth from 
the pond shore containing three pupse of Berosus, another hydrophilid genus, was 
brought into the laboratory July 16. It was not known at the time that it con- 
tained these pupse, and after it had served its purpose it was allowed to become dry 
and hard. When thrown out on August 15, it broke and revealed three live adult 
beetles, which could never have escaped through their own efforts. 
In The Canadian Entomologist for January, 1894, Ashmead published the 
descriptions of two new hymenopterous parasites from water beetles. These had 
been reared by H. F. Wickham — one from the pupa of a Gyrinus species and the 
other from the pupa of Dineutes assimilis. Similarly, half a dozen hymenopterous 
