270 BULLETIN OF THE BUREAU OF FISHERIES. 
those toward the middle of the lake, had enormous quantities of dead mayflies on their 
flat surfaces. In several cases the mayflies formed a solid cake 6 or 8 inches deep, the 
result of one season’s accumulation.” 
That they are also of prime importance as food for fishes has long been known. 
The anglers found it out first and used the soft bodies of the larger mayflies successfully 
for bait. Indeed, in view of the lack of acquaintance with our mayfly species existing 
at the present day, the many common names for them that were used by fishermen of 
old seems surprising. Such old-time books for anglers as Ronald’s Fly-Fisher’s Ento- 
mology (1877) abundantly attest this. 
Food studies have everywhere demonstrated how generally the nymphs of these 
big, burrowing mayflies are eaten by fishes. Forbes’s report (1888b) was one of the most 
extensive. He found that these larve constitute nearly one-tenth of all the food taken 
by the fishes that he studied. He says (pp. 484-485.) : 
From the order Neuroptera fishes draw a larger part of their food than from any other single group. 
In fact nearly a fifth of the entire amount of food consumed by all the adult fishes examined by me con- 
sisted of aquatic larve of this order, the greater part of them larve of dayflies (Ephemeridz), principally 
of the genus Hexagenia. These neuropterous larve were eaten especially by the miller’s thumb, the 
sheepshead, the white and striped bass, the common perch, 13 species of the darters, both the black 
bass, 7 of the sunfishes, the rock bass and the croppies, the pirate perch, the brook silversides, the stick- 
lebacks, the mud minnow, the top minnows, the gizzard shad, the toothed herring, 12 species each of 
the true minnow family and of the suckers and buffalo, 5 catfishes, the dogfish, and the shovelfish—7o 
species out of the 87 which I have studied. 
Among the above I found them the most important food of the white bass, the toothed herring, the 
shovelfish (51 per cent), and the croppies; while they made a fourth or more of the alimentary contents 
of the sheepshead (46 per cent), the darters, the pirate perch, the common sunfishes (Lepomis and Che- 
nobryttus), the rock bass, the little pickerel, and the common sucker (36 percent). * * * 
The larve of Hexagenia, one of the commonest of the “‘river flies,’’ was by far the most important 
insect of this group, this alone amounting to about half of all the Neuroptera eaten. They made nearly 
one-half of the food of the shovelfish, more than one-tenth that of the sunfishes, and the principal food 
resource of half-grown sheepshead; but were rarely taken by the sucker family, and made only 5 per 
cent of the food of the catfish group. 
Forbes’s studies were made on such material as happened to be at hand, without 
regard to times or seasons or conditions under which the fishes he studied had obtained 
their food. Subsequent studies of the food of the shovel-nosed sturgeon have made it 
necessary to qualify his statement as regards that fish. Wagner (1908, p. 28) says: 
The food of Polyodon consists, in Lake Pepin, entirely of plankton material, in largest part of ento- 
mostraca, but not unmixed with alge. There is one seeming, but only seeming, exception to this. 
Occasionally one finds the specimens of a morning’s catch largely gorged with larvae of Ephemerids. 
But in every such case it was found that ephemerid imagines appeared in vast numbers the same even- 
ing. It appears plain, therefore, that the larvae taken by Polyodon were captured on their journey to 
the surface of the water. 
Wagner (1908, p. 31) adds concerning the valuable rock sturgeon: ‘The food of 
this fish in Lake Pepin, in the summer at least, consists entirely of the larve of the 
Ephemerids;” but he does not specify what sort of mayflies. 
Pearse (1915) records that 7 of the 16 species of small shore fishes studied by him at 
Madison, Wis., had eaten mayflies, the percentages of this sort of food averaging as 
high as 58.3 per cent in the largemouth black bass and 40 per cent in the bluegill sunfish. 
In regularity of consumption and in amount consumed the young of mayflies were 
second only to midge larva. But Pearse also fails to specify the kinds of mayflies 
