214 



Usinger: Hemiptera 



Fig. 7:27. Male genital segments of Gerris in ventral view, a, 

 nofabilis; b, nycfalis; c, remigis (Drake and Harris, 1934). 



Key to California Genera of Gerridae 

 Nymphs 



1. Inner margins of eyes sinuate behind the middle . Gerris 



— Inner margins of eyes convexly rounded 2 



2. Tibia and first tarsal segment of middle leg with a 

 fringe of long hairs Halobates 



— Tibia and first tarsal segment of middle leg without a 

 fringe of long hairs 3 



3. First antennal segment long, subequal to the remaining 

 3 together Metrobates 



— First antennal segment much shorter than the remaining 

 3 together Trepobates 



Key to California Species of Gerris 



Antennae very long, more than 1/2 as long as body; 

 body length 15-20 mm.; reddish-brown; males with 

 venter roundly emarginate at apex (fig. 7:27a); widely 

 distributed, western North America (=rufoscutellatus 



Auctt.) notabilis Drake & Hottes 1925 



Antennae shorter, less than 1/2 as long as body; body 

 length less than 16 mm.; color dark brown to black; 



males with venter doubly emarginate at apex 2 



Large, robust species (11 mm. or more) 3 



— Smaller species (less than 11 mm. long) 4 



3. Color deep black; average size smaller, ranging from 

 11-13 mm., with relatively short legs and antennae; 

 male genitalia as in fig. 7:276, the eighth segment seen 

 from below dilated subbasally and the spines of 6th 

 segment reaching only halfway from base to apex of 

 inner lateral margin of 7th segment; Fresno, California, 

 C. J. Drake nyctalis Drake & Hottes 1925 



— Color brownish-black or even reddish-brown; average 

 size larger, H',2-16 mm., with relatively longer legs and 

 antennae (fig. 7:24). Male genitalia, fig. 7:27c, 8th 

 segment evenly rounded subbasally, spines of 6th 

 segment long; widely distributed, North America, com- 

 mon throughout California remigis Say 1832 



4. Anterolateral margins of pronotum without a pale stripe; 

 males with omphalium strongly elevated 5 



— Anterolateral margins of pronotum with a pale stripe; 

 males with omphalium scarcely elevated 6 



5. Notch at hind margin of 6th ventral segment of males 

 relatively shallow, the apices of 6th segment short, 

 reaching about to level of base of 8th (2nd genital) 

 segment as seen from below (fig. 7:28e); female con- 

 nexival spines abruptly incurved, not reaching level of 

 apex of 7th tergite; northwestern United States, British 

 Columbia incurvatus Drake & Hottes 1925 



— Notch at apex of 6th ventral segment in males deeper, 

 the apices of 6th segment longer and more attenuate, 

 surpassing level of base of 8th (2nd genital) segment 

 as seen from below (fig. 7:28c); female connexival 

 spines not abruptly incurved, reaching to apex of 7th 

 (1st genital) segment; widespread, North America, 

 scarce in California marginatus Say 1832 



6. First genital segment of males as broad as long, the 

 notch in middle at apex of 6th ventral segment sub- 

 rectangular (fig. 7:285); size small, 7-8.2 mm.; wide- 

 spread, North America buenoi Kirkaldy 1911 



— First genital segment of males distinctly longer than 

 broad, narrowed posteriorly, the median apical notch 

 of venter rounded; size relatively larger, S'^-lO'a mm. 



7 



7. First genital segment of male with conspicuous long 

 silvery hairs on either side of ventral surface (fig. 

 7:286); northern and western North America 



incognitus Drake & Hottes 1925 



— First genital segment of male without conspicuous long 



Fig. 7:28. Male genital segments of Gerris in ventral view, 

 a, gilletiei; b, incognitos; c, marginatus; d, buenoi; e, incurvatus 

 (Drake and Harris, 1934). 



