214 Transactions. — Zoology. 



Artificial Key to the Genera. 



The anal nervure meets the pobrachial at the root of the 



fore-wing . . . . . . . . . . Ephemera. 



The anal nervure remains separate from the pobrachial. 



Fifth joint of the hind tarsi very small or absent . . Atalophlcbia. 

 Hind tarsi distinctly 5-jointed. 



Hind tarsus shorter than the tibia. 



One claw blunt in each tarsus . . . . Colohurisciis. 



Both claws sharp in each tarsus .. .. Chirotonetes. 



Hind tarsus longer than the tibia . . , . Oniscigaster . 



Genus Ephemera, Linnaeus (1746). 



Imago. — Pronotum somewhat transverse. Legs all func- 

 tional, the hind pair the shortest, its tarsi 4- jointed ; fore 

 tibiae longer than the femur, shorter than the tarsus in the 

 male, equal to it in the female. Wing ueuration complete 

 and plentiful. Hind wings well developed, without a longi- 

 tudinal fold. Caudal setee very long in the male, moderate in 

 the female, the median about as long as the others. 



Subimago. — Quiescent for about twenty-four to thirty-six 

 hours, standing with erect connivent wings upon its hinder 

 legs, the fore legs prorect, off the ground, and the setae placed 

 close together. 



Nymph. — Fossorial, with tracheal branchiae upon the sides 

 of the segments. Legs short and strong, pilose, the tibiae 

 distally dilated and oblique, each hind tibia produced into a 

 spine. Head with two conical projections in front. 



Distribution. — North Temperate and Indian regions. 



Ephemera hudsoni. 



Ephemera hudsoni, McLachlan, Eut. Mo. Mag., 1894, p. 270; 

 Hudson, Man. N.Z. Entomology, pi. 16, fig. 4. 



Imago (male). — Body castaneous, the segmental divisions 

 narrowly darker, paler beneath. Legs pale-yellowish, the 

 anterior femora with a short blackisli line internally, their 

 tips and those of the tibise and tarsal joints darker. Anterior 

 wings vitreous, iridescent, the costal margin dark reddish- 

 brown. Posterior wings vitreous, without markings. Caudal 

 setae (?). Length of body (?) ; of anterior wings, IQimm. ; 

 expanse of wings, 41 mm. 



Subimago (male). — Body greyish-brown, with the seg- 

 mental divisions narrowly darker. Legs pale-yellowish, with 

 the articulations blackish. Outer caudal setae long, the 

 middle rudimentary. Anterior wings subopaque, pale-greyish, 

 with two oblique, transverse, smoky bands. Posterior wings 

 with a smoky, median, oblique band. Length of the body, 

 20 mm. ; expanse of the wings, 41mm. 



Subimago (female). — Eather larger and more robust than 



