428 NEW YORK STATE MUSEUM 



1888 Hexagenia spJ (probably va r i a b il i s and bilineata) Forbes, 

 State lab. nat. List. Bui. 3. 2:484-85 (estimate of tbe value of Hexa- 

 g e n i a larvae as food for fisbes, based on the examination of tbe stomach 

 contents of 1221 fishes, representiug 87 species, 63 genera, and 25 fami- 

 lies: Hexagenia larvae constitute nearly one tenth of all the food 

 taken). Summary in Insect life. 1888. 1:158-61 



This species was much less numerous than the other six whose life his- 

 tories are discussed here. It was found only along Little Clear creek. 

 An occasional subimago was seen in early morning leaving the water and 

 flying weakly to some neighboring tree trunk to rest. A single specimen 

 was taken on the outside of a trap lantern in the morning twihght. A 

 few were picked from the sides of the hatchery building, where they were 

 conspicuous on account of their size. 



The nymphs were easily obtained from the bottom of the creek with 

 a sieve net. They were obtainable throughout the season, this species not 

 having a limited period of emergence, as H. bilineata seems to have. 

 Nymphs taken incidentally while collecting, were reared at various times 

 from June 26 to Aug. i. They were associated in the creek bed with 

 Ephemera varia, described below, but were very much less num- 

 erous. In our breeding cages the subimago emerged one night and 

 transformed to the imago the night following. 



Nymph. PI. 16, fig. 2, 3. Length of body 27 mm; setae 12 mm more; 

 abdomen of male 18, of female 21 mm; antenna 4.5 mm. 



Color yellow, with some paler longitudinal markings on the thorax ; a 

 series of mushroom-shaped marks on abdominal segments 6-9. 



Head compressed ; a shelf like prominence above the base of each an- 

 tenna, straight on its front border, round on its exterior side; the 

 frontal prominence semi-elliptic ; mandibular tusks long, stout, upcurved, 

 with a line of hairs on their supero-external margin. 



Antennae at base, and the sharp edges of the legs, and the lateral 

 margins of the prothorax, densely clothed with long yellowish hairs. 

 The antennae are bare at the tips and do not surpass the extended fore 

 tarsi. 



Legs (pi. 16, fig. 3) short, stout, twisted, flattened, closely applied to 

 the sides of the body, and well adapted for burrowing ; femora and tibiae 

 scapulate ; the tibia produced at its apex into a terminal burrowing hook 

 and scraper, the edges bearing a stifl'line of hairs ; the hind foot chelate, 

 the distal angle of the tibia forming with the opposed tarsus a pincer. 



Gills on segments 1-7 ; gill of the first segment small and shaped like 

 a tuning fork; of the six following segments large, of a rich purplish 

 color, two leaved, the leaves similar, lanceolate, and densely fringed with 

 minute linear respiratory filaments, which are as long as the greatest 

 width of the gill leaf. On the flat side of each gill leaf is a yellow, longi- 

 tudinal median line closely bordered on either side by a line of black. All 

 the gills are directed over the back, where they are gently waved back 

 and forth in intermittent, graceful motion. 



One of the largest of our May flies; generally distributed over the 



United States east of the Rocky mountains. 



