Lake Maxinkuckee, Physical and Biological Survey 9 



the evening a great many were seen flying about and on the grass. 

 They leave their cast-off skins on the grass a few steps back from 

 the lake shore. None could be seen on June 4, but on June 22 one 

 was seen, the last of the season. 



All the above applies to a long, blackish, rather robust species 

 with three long caudal setae. 



On June 7, were seen a few of a second species, more slender 

 than the other and with only two caudal setse. 



It is a common belief about the lake that many fishes die as a 

 result of gorging themselves with May-flies, but this opinion was 

 not sustained by the examination which was made of the stomachs 

 of a considerable number of fishes found dead during May-fly 

 time. 



In addition to the larger May-flies of early summer, a diminu- 

 tive form of a light bro'vsTi color, but semitransparent, was present 

 in immense numbers in autumn, emerging one night, and laying 

 their eggs on the surface of the water during the next day and 

 evening. These were present in such numbers that they formed 

 regular drifts about the base of a large bullseye lamp set on the 

 pier, the insects flying toward the pier light and becoming tangled 

 up together by their long and delicate caudal stylets. Although 

 probably as abundant numerically as the large May-flies of spring, 

 these minute forms did not attract the attention that the former 

 did, because of their pigmy size and inconspicuous coloration. The 

 lisping of the minnows and other little fishes such as skipjacks, 

 along shore on fine autumnal evenings, was caused by their snap- 

 ping at these little insects as they deposited their eggs on the water 

 surface. 



A remarkable feature about the May-flies is their habit of 

 moulting after the wings have formed, and after they have flown a 

 little distance from the lake. It is astonishing how such a thin 

 transparent membran-: as their wings can be shed. The dark, 

 heavy species alights on the grass to make this last change but a 

 light transparent species of late summer is often not able to shed 

 the skin from its caudal stylets, but bears the entire cast-off clothes 

 on these, and is thus greatly impeded in its flight. 



The larvae of some of the large dark May-flies feed on the 

 softer portions of old, dead leaves, in the bottom of the water, and 

 some of them will, in a very short time, completely skeletonize a 

 leaf, leaving only the delicate lace-work of the veins. 



