82 



Day: Ephemeroptera 



Every effort should be made to avoid any possibility 

 of confusion in associating nymphs and adults of a 

 single species; therefore the nymphal skins and 

 imagoes of the same species are finally added to the 

 same vial of 70 per cent alcohol wherein a half-dozen 

 similar nymphs had been placed originally. 



Mature nymphs of certain species may be transported 

 over quite long distances for rearing in the aquarium. 

 At the point of collection, several dozen mature 

 nymphs may be placed in a single six-by-eighteen- 

 inch aluminum screen cylinder. During the day's 

 collecting, this cylinder is half immersed in the 

 stream as for field rearing. At the end of the day, the 

 screens are taken from the stream and placed in three- 

 gallon aluminum milk cans having about six and 

 one-half inch mouths, the cans being two-thirds filled 

 with fresh and well-aerated stream waters. The cans 

 are well wrapped with thick cotton cloths which, 

 when thoroughly wetted, provide quite cool tempera- 

 tures through evaporation. By traveling during the 

 cool evening hours, with an occasional stop for re- 

 wetting cloths, even many fast-water species may 

 be safely carried more than two hundred miles and 

 reared in the aquarium. 



A successful mayfly rearing aquarium in use for 

 several years is eighteen-by-thirty inches in size with 

 a depth of nine inches, constructed of glass and 

 stainless steel. A strong current of water is produced 

 in the tank by Samuel S. Gelber Company's stainless 

 steel, rubber centrifugal pump No. 205, with sheets 

 of heavy plastic arranged in the aquarium to create 

 areas of quiet water, slow current, and rapid current. 

 A single brick stands on end for the use of nymphs 

 which clamber out of the water for emergence. 



The aquarium must be kept clean, and the nymphs 

 reared in water brought from the stream where they 

 were collected. The oxygen level of the water in the 

 aquarium should be maintained through the use of a 

 Venturi tube at the discharge end of the Gelber pump, 

 or by continuous operation of a Marco air pump, or 

 equivalent. A small amount of sand and coarse gravel 

 should be scattered over the bottom of the aquarium, 

 and a half-dozen rocks from the collecting stream 

 disposed about the tank. With water coils or floating 

 heater, water temperatures can be held within a few 

 degrees of stream temperatures. 



Any number of well-known genera may be reared 

 together in one tank since the adults are easily 

 separated; however, nothing but confusion comes forth 

 from a mixture of the nymphs of closely allied species. 



CLASSIFICATION 



In the taxonomy of the adult mayflies, the arrangement 

 and form of the wing veins is of utmost importance. 

 The following keys are based on those prepared by 

 Dr. J. R. Traver for Biology of Mayflies, Needham, 

 Traver, and Hsu (1935). The system of wing venation 

 used herein is that of Dr. James G. Needham, and is 

 shown in figure 3:2a. In all keys Cu, is used inter- 

 changeably with CuA and Cu, with CuP. The keys 

 which follow are for the families and genera of may- 



flies of the United States and Canada, and for the 

 California species. 



Key to the Families of the Order Ephemeroptera 

 Adults 



1. Veins M and Cu, of fore wing strongly divergent at 

 base, with M, strongly bent toward Cu, basally; outer 

 fork (Of) in hind wing wanting (fig. 3:26); hind tarsi 



4-jointed EPHEMERIDAE 



Veins M and Cu, little divergent at base and fork of 

 M more nearly symmetrical; outer fork (Of) of Rs in 

 hind wing present or absent; hind tarsus 4- or 5-jointed 



2 



2. Hind tarsus with 5 freely movable joints; cubital inter- 

 calaries in 2 parallel pairs, long and short alternately; 

 venation never greatly reduced (fig. 3:2c); eyes of the 

 male simple HEPTAGENIIDAE 



— Hind tarsi with 3 or 4 freely movable joints; cubital 

 intercalates not as above (except in Metre top inae); 

 venation sometimes greatly reduced (fig. 3:2d); eyes of 

 male often divided BAETIDAE 



Nymphs 



1. Mandible with an external tusk projecting forward and 

 visible from above the head (except in Neoephemerinae) 

 (fig. 3:2c) EPHEMERIDAE 



— Mandible with no such tusk, except in some species 

 of P araleptophlebia 2 



2. Head strongly depressed; eyes dorsal 1 (fig. 3:2/) . . . 



HEPTAGENIIDAE 



— Head not strongly depressed; eyes lateral (fig. 3:2<?) 



BAETIDAE 



Family EPHEMERIDAE 



Key to the Genera 



Adults 



1. Costal cross veins normally developed 2 



— Basal costal cross veins vestigial or wanting 



Neoephemera McDunnough 



2. Marginal veinlets absent 3 



— Marginal veinlets present 4 



3. Middle and hind legs reduced to functionless, membran- 

 ous vestiges, but with all leg parts discernible 



T ortopus Needham & Murphy 



— Middle and hind legs aborted beyond the trochanters 



Campsurus Eaton 



4. Cubital intercalaries simple Ephoron Williamson 



— Cubital intercalaries widely forking 5 



5. Cubital intercalaries 1 or 2, long and deeply forked 



Potamanthus Pictet 



— Cubital intercalaries shorter and with shallow forks, 

 more like marginal veinlets, decurrent from vein Cu, 



6 



6. Cross veins somewhat crowded at and below bulla; 

 wings with a variable pattern of dark spots 



Ephemera Linnaeus 



— Cross veins not crowded at bulla; wings with no pattern 

 of dark spots 7 



7. Penes tubelike, tips not incurved. . . . Pentagenia Walsh 



— Penes broader at base than apex, tips more or less 

 incurved (fig. 3:3rf) Hexagenia Walsh 



'Certain Leptophlebiinae, of family Baetidae, which may seem 

 to fall here, have gills of each pair filiform or lamelliform, where- 

 as in Heptageniidae the upper member of each gill pair is platelike 

 the lower member fibrillate. 



