101 



Day: Ephemeroptera 



Nymphs 



1. Gills on segments 1-5 only; lateral tails bare, or at the 

 most with only a few inconspicuous setae 



Baetodes Needham and Murphy 



— Gills on segments 1-7 2 



2. Gill lamellae double (often with a mere recurved flap 

 on ventral or dorsal surface) on abdominal segments 

 1-6 or 1-7 3 



— - Gill lamellae single on all abdominal segments .... 5 



3. Tracheae of gill lamellae palmately branched; second 

 pair of wing buds absent Cloeon Leach 



— Tracheae of gill lamellae pinnately branched; second 

 pair of wing buds present 4 



4. Double part of gill a flap on ventral surface (fig. 3:24m); 

 maxillary palp 2-jointed Callibaetis Eaton 



— Double part of gill a flap on dorsal surface; gills double 

 on 1-7; maxillary palp 3-jointed (fig. 3:24o) 



Centroptilum Eaton 



i 5. Tails 2 6 



— Tails 3 7 



6. Second pair of wing buds absent; labium as in figure 

 3:28a Pseudocloeon Klapalek 



, — Second pair of wing buds present (bicaudatus, and the 

 propinquus group) (fig. 3:24n) Baetis Leach 



7. Middle tail shorter and weaker than outer ones 



Baetis Leach 



— Middle tail practically as long and stout as outer ones 



8 



8. Second pair of wing buds present. . . Centroptilum Eaton 



— Second pair of wing buds absent 9 



9. Labial palp 3-jointed, form of distal segment as in 

 Centroptilum Neocloeon Traver 



— Labial palp 2-jointed 10 



10. Labrum with median notch on anterior margin; distal 



margin of apical segment of labial palp pointed on 

 outer side and rounded on inner side (fig. 3:286) . . . 

 Paracloeodes Day 



— Labrum without median notch on anterior margin; distal 

 margin of apical segment of labial palp squarely 

 truncate with deep V on inner margin (fig. 3:28c) . . . 



Apobaetis Day 



Genus Callibaetis Eaton 



Distributed in all parts of California in lakes, streams, 

 and ponds, the nymph is strictly a lotic water form, 

 dainty and gracefully streamlined and an excellent 

 swimmer. For some general features of adult Calli- 

 baetis see figure 3:24p, <?• 



Key to the California Species 

 Adults 



1. Cross veins of fore wing behind the vitta (or behind 

 the fourth longitudinal vein) relatively few in number — 

 only about 15-25; usually none very near the hind 

 margin; usually a single irregular row of them across 

 the wing 2 



- Cross veins of fore wing behind the vitta more numer- 

 ous — about 35-60 of them; usually several are close to 

 the hind margin; 2 or more very irregular rows of them 

 across the wing 6 



2. Intercalates of middle area of outer margin of fore wing 

 usually occur in pairs 3 



- Intercalates of middle area of outer margin usually 

 occur singly 5 



3. Wing 5 l / 2 to 7 mm. in length; in wing of female, several 

 brownish clouds on veins behind vitta, also on hind 

 margin; cross veins brown in male, locality given as 

 "California" pictus (Eaton) 1871 



- Wing 7-9 mm. in length; no such distinct brown clouds 

 behind vitta in wing of female; cross veins in wing of 

 male pale or brownish 4 



Fig. 3:25. Hind wings of Baetis. a. bicaudatus; b, tricaudatus; 

 c, intermedius (W. C. Day). 



4. Abdominal tergites 5, 6, and 9 of male with large pale 

 areas; in female, tergites 1, 4, 7, and 8 almost wholly 

 dark brown, others pale with dork markings; cross veins 

 brown in male wing (fig. 3:24;'); widespread 



pacificus Seemann 1927 



— Abdominal tergites 7 and 9 of male with large pale 

 areas; in female all tergites pale brown; cross veins 

 in wing of male pale; Redlands . . . signatus Banks 1918 



5. Tails dark brown at the joinings (fig.3:24i); widespread 



calif ornicus Banks 1900 



— Tails wholly pale or pale yellowish only at joinings; 

 Sacramento Valley montanus (Eaton) 1885 



6. Intercalates of the middle area of the fore wing usually 

 occur singly 7 



— Intercalates of the middle area of the fore wing usually 

 occur in pairs 8 



7. Clouds present in disc and along outer margin of wing 

 of male;tails blackish at joinings;San Bernardino Mts. 

 and Alameda County carolus Traver 1935 



— Wings of male not pigmented; tails faintly yellowish 

 at joinings; San Joaquin and Sacramento valleys 



traverae Upholt 1937 



8. Vitta in wing of female dark brown, and many clouds 

 along veins and outer margin; male fore wing 12 mm. in 

 length; San Joaquin Valley and San Francisco 



hageni (Eaton) 1885 



— Vitta in wing of female irregularly mottled with reddish 

 brown; no clouds on veins or outer margin; male fore 

 wing 9J,£ mm. in length; Marin and Alameda counties 



hebes Upholt 1936 



Insufficient data are available to make possible a 

 key to the nymphs of the California Callibaetis that 

 would be of practical value in the separation of 

 species. For the general appearance of the Callibaetis 

 nymph see figure 3:26a. The distinctive labium is 

 shown in figure 3:266. The following nymphs have 

 been reported from California: 



C. californicus Banks 

 C. carolus Traver 

 C. hebes Upholt 

 C . montanus Eaton 

 C. pacificus Seeman 



Genus Baetis Leach 



Members of this genus occur almost wherever running 

 water is found in California. The small nymphs, not 

 longer than 8 mm., are very adaptable, living in the 

 open waters of streams in currents ranging from slow 

 to very swift. 



Key to the California Species 

 Male Adults 



1. Hind wing with strong, curved costal projection, much 

 as in Centroptilum (fig. 3:27e,;'); central California 

 coastal leechi Day 1954 



— Hind wing without strong, curved costal projection . 2 



2. Hind wing with 3 longitudinal veins of about equal 

 length 3 



