116 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 

 Hexagenia bilineata Say. 

 (PL XIII, Fig. 1). 



Nymphs of this species were first taken on June 6, 1912, by dredging in water 

 15 to 45 feet deep. The bottom was very muddy. These were taken to the lab- 

 oratory and about ten were placed in a breeding-jar, f filled with soft muck. The 

 nymphs immediately began to burrow, using their fore-legs to displace the mud. 

 They were able to bury themselves in a remarkably short time. At first the gills 

 were left partly exposed and the position of the creatures could be detected by the 

 waving motion of these in the thin mud. They remained this way for a short time, 

 but later on only the round openings of their burrows could be seen. 



The first subimago to emerge from the breeding-jar was on July 3, and others 

 followed during July and August. One nymph was stiU alive in the jar when I 

 stopped my work on September 9th. On June 13th the first subimago was captured 

 at large and from this on a few subimagos and imagos were taken at various times, 

 but not imtU June 28th did they appear in large numbers. On this date about 

 dusk, a large number of females were discovered flying up and down a long narrow 

 channel between an island and the mainland. They dipped down frequently to 

 deposit their eggs and many fell victims to hungry fish. For a couple of weeks 

 after this, this species appeared in immense numbers. They commenced their 

 flight about three-quarters to half an hour before dark and swarmed about the tree- 

 tops, forty feet high. None were observed after July 23rd. On July 12 I caught a 

 female just after copulation and held her over a jar of water, touching her abdomen 

 to the water occasionally and she deposited a large number of eggs. The water 

 was changed from time to time to keep it from becoming stagnant, and on August 

 17 a number of very small nymphs appeared. This was a period of thirty-six days. 



Description of nymph. Length of body 30-35 mm.; setse 13-15mm.; anten- 

 nae 5-6mm. Head yellowish with the dorsal surface between ocelli and between 

 eyes entirely brown, or in some cases lighter along median line and posterior 

 margin. Antennae very hairy at joints of basal halves, while apical halves are en- 

 tirely bare and become very slender. Margin and base of frontal piece hairy. 

 Clumps of hairs between eyes and bases of antennae, in front of lateral ocelli and 

 posterior to eyes.' Mandibular tusks, f length of antennae, upcurved, brown at 

 tips, and with three longitudinal rows of hairs. Prothorax brown for the most part 

 dorsally. Each abdominal segment has a large almost triangular brown area 

 with two light areas within it. These light areas often reduced to mere stripes. 

 Ventrally on segments 6 to 8 a faint median longitudinal dark streak, while on 

 9th segment there are two lateral streaks. SetsB of about equal length and very 

 heavy at joints for entire length. GiUs and legs of the usual Hexagenia type. 



Ephemera simulans Walker. 



For some inexplicable reason I was unable to find Ephemera nymphs at Go 

 Home Bay, although the imagos were very abundant and the shore was strewn 

 with the nymph sloughs. Dredging failed to bring them up, although Hexagenia 

 nymphs were dredged up almost everywhere in Go Home Bay. However, Mr. 



