98 



Day: Ephemeroptera 



Fi 

 lata; 

 Hsu, 



g. 3:23. Male 

 c, inermis: d, 



1935). 



genitalia of Ephemerella. a, euterpe; b, macu- 

 mollitia; e, infrequens (Needham, Trover, and 



Genus Ephemerella Walsh: Inixaria Group 



Key to the California Species 



Adults 



1. Second joint of male forceps not distinctly swollen 

 apically; thoracic notum deep blackish brown; a dark 

 spot at base of fore wing (fig. 3:23c) 



inermis Eaton 1884 



— Second joint of forceps distinctly swollen apicaliy; 

 thoracic notum reddish brown or yellow-orange 2 



2. Thorax deep yellow and orange; 24-26 spines on the 

 penes, of which 8-10 are at the apex (fig. 3:23<i) .... 



mollitia Seemann 1927 



— Thorax deep olive brown to red-brown; 14 to 16 spines 

 on the penes of which 4-5 are at the apex (fig. 3:23e) 



infrequens McDunnough 1924 



Nymphs 



1. Pronotum with distinct pale markings; pale submedian 

 spots present on the posterior margins of the abdominal 

 tergites; dorsal spines absent 2 



— No such pale markings on the pronotum; no pale sub- 

 median spots on the posterior margins of the tergites; 

 dorsal spines absent; widespread 



infrequens McDunnough 1924 



2. Lateral extensions of the abdominal segments marked 

 with a dark median transverse band; tails with several 

 median and apical dark bands; widespread 



inermis Eaton 1884 



— Lateral extensions of abdominal segments with no such 

 dark median band; tails banded only at the base; wide- 

 spread mollitia Seemann 1927 



Genus Ephemerella Walsh: Hecuba Group 



The group consists of one unique species, E. hecuba 

 Eaton 1884, which is found generally distributed at 

 all elevations in northern California. 



Adult. — On pleural fold of segments 4 to 7 are small 

 fingerlike projections directed backward and slightly down- 

 ward. The length of the fore wing is 14 mm., head and 

 thorax black- brown. Dorsally, the abdomen is dark yellow- 

 brown and, ventrally, whitish (fig. 3:156). 



Nymph. — Body greatly flattened and hairy; a short tubercle 

 on the dorsal surface of the middle coxa; all femora with 

 large, single acute spine at apex; gill on segment 4 oper- 

 culate (fig. 3:19c). 



Genus Ephemerella Walsh: Simplex Group 



Key to the California Species 



Nymphs 



Tergites 2-9 with fine, sharp pointed, paired submedian 

 spines; segments 3-9 with posterolateral spines (fig. 



3:27n); Madera County soquele Day 1953 



Tergites 4-8 with wartlike paired submedian projections; 

 segments 5-8 with posterolateral spines; Placer and 

 Mono counties delantala Mayo 1952 



Genus Ephemerella Walsh: Bicolor Group 



This group is represented in California by E. lodi 

 Mayo 1952 of which only the male and female adult? 

 are known. Wings are amber-tinted and venation yel- 

 low. Tergites one to three are brown and four to ten 

 yellow with posterior margins washed with brown. 

 Found in Amador County. 



Ungrouped California Species: Part I 



Unassigned to any group is a very unusual species, 

 E. pelosa Mayo 1951, known only in the nymphal 

 stage and found to date only in California. A very 

 hairy species, it is distinguished by paired tufts of 

 short hairs in the position ordinarily occupied by 

 paired abdominal spines on the tergites; sternites 

 three to eight are covered with long, white hairs 

 that radiate from the centers of the posterior margins 

 of sternites three to seven, and from the anterior 

 margin of sternite eight. Found in Fresno and Alpine 

 counties. 



Ungrouped California Species: Part II 



Ephemerella heterocaudata McDunnough 1929, was 

 assigned in "Biology of Mayflies" to the serrata 

 group. In the description of E. spinosa Mayo 1951, 

 this species was referred to the needhami group by 

 Dr. Mayo. 



E. spinosa Mayo is here regarded as a synonym of 

 E. hystrix Traver, and these two species should 

 probably be placed in a new group of Ephemerella 

 because they have similarities to each other that 

 seem more positive than their attachments to present 

 groups. 



Descriptions have been given for both male adult 

 and nymph of E. heterocaudata but only the nymphal 

 form is known for E. hystrix. Both species have been 

 collected in California and can be quickly separated 

 from all other California species of the genus Epheme- 

 rella since the length of the center tail of adult and 

 nymph considerably exceeds that of the outer tails; 

 tails of the nymph have whorls of spines at each 

 joining. 



