1()6 Transactions. — Zoology. 



Much diversity is exhibited in the number and relative 

 propoi-tions of the caudal setae. 



The term "nymph " is used to denote all the subaqueous 

 stages in the development of the young after hatching. In 

 general form they resemble the adult. The tracheal branchiae 

 are movable, membranaceous, or filamentose appendages to 

 the integuments, enclosing branching tracheae. The term 

 " subimago " is used to denote the penultimate stage in the 

 life of such of the Eplicmeridoi as moult once, after direct 

 respiration through the stigmata has been established, and 

 the wings have become fully expanded. The chief points by 

 which this stage can be distinguished from the adult are — the 

 diilness of the integuments, particularly of the wings ; the 

 ciliolate terminal margin of the wings in many genera ; the 

 shortness of the fore legs ; the greater hairiness and shortness 

 of the caudal setae ; the less protuberant and less highly 

 coloured ocelli ; and in the male the marked shortness and 

 stoutness of the limbs of the forceps. 



The above account is condensed from Eaton's Monograph. 



In the " Eevisional Monograph of Eecent E'phemeridce, 

 or Mayflies," by the Eev. A. E. Eaton, M.A., pubhshed in the 

 "Transactions of the Linnaean Society," London, 1888, the 

 following genera are given as represented in New Zealand : — 



Epliemera (1 species). — Undescribed. 



Atalophlehia (3 species). — A. dentata, A. nodularis, 



A. scita. 

 Coloburus (1 species). — C. humeralis. 

 Siphlurus (1 species). — Doubtful. 

 Oniscigaster (1 species). — 0. wakefieldi. 

 Chirotonetes (?) (1 species). — C. ornatus. 



Thus it will be seen that six species are described, but 

 of these the nymph stage of only one {Oniscigaster wakefieldi) 

 is known. 



During the present summer I succeeded in rearing a num- 

 ber of insects of two species of Atalophlehia from the nymph 

 stage, and am consequently able to describe all three stages. 



Genus Atalophlebia, Etn. (1881). 



Adult. — Hind wing in front somewhat arched, the summit 

 of the arch obtusely subangular, situated usually before the 

 middle of the curve ; subcosta (2) strongly arched, meeting 

 the margin very obliquely ; radius (3) nearly straight, consti- 

 tuting, as it were, the cliord of the arch described jointly 

 by the subcosta and the portion of the margin included 

 between its extremity and the radius ; hence, while the narrow 

 marginal area is broadest at the base and acuminate at its 

 termination, the submarginal area is bi'oadest either in the 



