2°10 NEW YORK STATE MUSEUM 
common in a pond on the campus at Lake Forest, and there I 
have observed its habits for several years. 
The larvae are free swimming and are found most abundantly 
beyond the line of the shore vegetation. They are entirely 
transparent, except for two pairs of air sacs and some pigment 
in the eyes, and, generally, food in the alimentary canal, ap- 
pearing as a dark line through the middle of the body. Their 
transparency doubtless secures them some immunity from ene- 
mies. I have experimented with feeding them to a hungry 
nymph of a dragon fly Libellula pulchella. Placed 
in the nymph’s mouth, they were eaten with avidity, but, placed 
thickly in the water with it and swimming around within easy 
reach, none were captured or even reached after by the nymph. 
It was probably unable to see them, for it quickly seized water 
boatmen (Corisa) when substituted for the Corethra larvae. 
I yery much doubt whether the trout can see them. If they 
are aS abundant in Bone pond as they often are in my campus 
pond, even the considerable number shown in the table, might, 
I think, have been taken in the straining of the water through 
the gill rakers, without selection of any individuals for capture. 
The pupae of Corethra are at first likewise transparent and 
free swimming, but soon rise to the surface and float there, like 
‘Chironomus, and just before transformation, become darker 
colored. The imagos settle on low vegetation around the bor- 
ders of the water, or rise, dancing in swarms in sheltered and 
sunny places. The females deposit the eggs on the surface of 
the water, laying them down flatwise, in a spiral held together 
by scanty gelatine. 
Among insects these larvae are the most independent of the 
shore yegetation. They feed on free swimming unicellular 
plants and animals. In my campus pond during April and May 
{the months of my observation) they live chiefly on a species of 
Peridinium, with a sprinkling of other flagellate infusorians. 
Specimens taken freshly from the pond generally show a dis- 
tinct brown streak through the middle of the body, due to the 
Peridinia eaten. They are not incapable of disposing of much 
