90 



Day: Ephemeropterq 



Fig. 3:11. a, Ephemerella sp., wings; b, Ameletus dissitus, 

 hind wing; c,d, anterior and posterior lamellae of first nymphal 

 gill of Siphlonorus sp.; e, Ameletus sp., maxilla of nymph; f, 

 Isonychia velma, fore leg of nymph (a,e, Needham, Traver and 

 Hsu, 1935; b.f, Day; c,d, Spieth, 1933). 



4. Abdominal segments 5-9 greatly expanded laterally 



Siphlonisca Needham 



— Abdominal segments 5-9 normal, not greatly expanded 

 lateral ly 5 



5. A pincerlike process near tip of labial palp; no pecti- 

 nate spines on crown of maxilla 



Parameletus Bengtsson 



— No such pincerlike process on labial palp; a fringe of 

 pectinate spines on upper margin of maxilla (fig. 3: lie) 



Ameletus Eaton 



Genus Ameletus Eaton 



This genus is widely distributed in California at all 

 elevations. Although found in many fast streams the' 

 nymph often seeks the quieter parts. It is a fine; 

 swimmer. Because of insufficient data a key to the 

 nymphs of California species is impractical. 



Key to the California Species 

 Male Adults 



1. Several cross veins in fore wing widely margined with] 

 brown, so that wing appears speckled (fig. 3:15a); 



Amador County amador Mayo 1939 



No widely margined cross veins; wings not- speckledj 



." 2 



2. Ganglionic areas of abdominal sternites strongly marked 

 with black or brown 3 



— Ganglionic areas of sternites not strongly marked with 

 black or brown 4 



3. A single long slender spine attached to inner margin of 

 each division of penes; abdominal tergites yellow (fig. 

 3:12a); Alameda County, Napa County, and "San Gero- 

 nimo" dissitus Eaton 1885 



— Penes without such spines; abdominal tergites yellow- 

 brown (fig. 3:13a); southern California, montane .... 



velox Dodds 1923 



4. Wings strongly brown tinted 5 



— Wings clear, very faintly brown, or milky 6 



5. Apical ends of penes rounded, stimuli absent (fig. 

 3: 136); Redwood Belt and Alpine County 



shepherdi Traver 1934 



— Apical ends of penes fine pointed, directed outward; 

 short, straight, fine stimuli present (fig. 3:14a); montane 



validus McDunnough 1923 



6. Wings faintly milky; ganglionic areas of sternites 

 faintly dark; stimuli of penes straight; second joint of 

 forceps bent strongly inward at base (fig. 3:126); coast- 

 al and Sierra imbellis Day 1952 



— Wings vitreous or faintly brown; ganglionic areas of 

 sternites opaque white; stimuli of penes bent outward 

 at right angles at tips (fig. 3:12c); central California, 

 coastal facilis Day 1952 



Genus Siphlonurus Eaton 



S. spectaiilis is a very common species of general 

 distribution, but collection data indicates it is restrict- 

 ed to the lower elevations. S. columbianus has been 

 found only at elevations above 4,000 feet. The per- 

 fectly streamlined nymphs of this genus attain lengths 



Fig. 3:12. Male genitalia of Ameletus. a, dissitus; 

 b, imbellis; c, facilis (Day, 1952). 



