210 NEW YORK STATE MUSEUM 



€ommon in a pond on the campus at Lake Forest, and there I 

 liave 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 

 irymph of a dragon fly L i b e 1 1 u 1 a p u 1 c h e 1 1 a . 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 very 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 vegetation. They feed on free swimming unicellular 

 plants and animals. In my campus pond during April and May 

 (the months of ray 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 



