216 



Usinger: Hemiptera 



Fig. 7:29. a, Rhagovelia distincta. Champion, female, Davis, Yolo County, California, October 

 24, 1942, (R. L. Usinger); b, Microvelia californiensis McKinstry, female, Mokelumne Hill, 

 Calaveras County, California, May 29, 1931 (R. L. Usinger). 



needs careful study to correlate winged and wingless 

 forms and to establish the identity or differences 

 between our species and various poorly known but 

 earlier described species from Central America and 

 the West Indies. Drake and Hussey (1955) have made 

 a start on this but their treatment of incerta (Kirby) 

 as a subspecies of pulchella Westw. is not in accord 

 with the current definition of subspecies. 



Rhagovelia has received more attention (Gould, 

 1931), but the geographical variation in southern 

 and western species was treated under several "vari- 

 eties" of R, distincta. Either these "varieties" are 

 geographical subspecies (in which case several more 

 populations could be differentiated from California) 

 or distincta is a single extremely variable species. 

 A third possibility is that each slightly different 

 population represents a distinct local species but 

 there seems to be no evidence for this at the moment. 

 Dimorphism is even more striking in Rhagovelia than 

 in Microvelia because of the great differences between 

 the sexes (see figs. 7:29, 7:30). In the macropterous 

 females the pronotum is often produced backward and 

 upward into a long, curved, blunt spine. 



For the present, keys are offered only for apterous 

 males. This is because the apterous forms are most 

 commonly encountered and are the best known. Also 

 the thoracic sclerites present the most obvious char- 

 acters and therefore have been used in the best 

 existing keys (Parshley, 1921; Bueno, 1924). I am 

 indebted to A. P. McKinstry for making available his 

 unpublished key to Microvelia, parts of which have 

 been used in the present key. 



Key to the Nearctic Genera of Veliidae 



1. Middle tarsi deeply cleft, with leaflike claws and 

 plumose hairs arising from base of cleft. Subfamily 

 Rhagoveliinae 2 



— Middle tarsi not deeply cleft and without plumose hairs 

 arising from base of cleft 3 



2. Hind tarsi 2-segmented, the basal segment very short; 

 apterous, marine, tropical American in distribution 



Trochopus Carpenter 1898 



— Hind tarsi 3-segmented, the basal segment very short; 

 apterous or macropterous (fig. 7:29a). Cosmopolitan, 

 riffles of rivers Rhagovelia Mayr 1865 



3. Tarsal formula 3:3:3. First antennal segment distinctly 

 longer than the others. Subfamily Veliinae 



Velia Latreille 1807 



— Tarsal formula 1:2:2. First antennal segment subequal 

 to others (fig. 7:296) . . Subfamily Microveliinae ... 4 



4. Middle legs nearly equidistant from other two, tarsal 

 claws normal Microvelia Westwood 1834 



Fig. 7:30. Rhagovelia obeso Uhler. a, cleft tarsus of middle 

 leg; b, same, with fringed hairs spread; c, one of the fringed 

 hairs enlarged; d, apterous male (Hungerford, 1920). 



