332 



Leech and Chandler: Coleoptera 



Fig. 13:28. Hydraenidae, larvae, o, Limnebius truncatellus; 

 b, Hydraena pensylvanica; c, Ochthebius fossatus; d, Hydraena 

 sp., labrum and clypeus of larva (a, D'Orchymont, 1913; b~d, 

 Richmond, 1920). 



Eureka County, Nevada, and from one at Amedee, 

 Lassen County, California; it has since been reported 

 from other Nevada hot springs (see La Rivers, 1950). 

 A species allied to 0. rectus LeConte is common in 

 the saline pools at Bad Water, 276 feet below sea 

 level in Death Valley, Inyo County, California, and 

 has been recorded from other waters in the valley 

 (Thorpe, 1931). One apterous species, O. vandykei 

 Knisch, is known only from the intertidal zone of the 

 Pacific Coast of North America, from British Columbia 

 south at least to San Luis Obispo County, California. 

 It occurs in narrow cracks in and between the rocks, 

 and is allied to species of similar habitats on the 

 west coast of Europe and the Mediterranean. 



The genus Ochthebius, with many subgenera, is 

 dominant in Europe and in North America, but is 

 represented in Africa, Madagascar, India, Siberia, 

 and Australia. One species is reported from Central 

 America and one from South America, but the hiatus 

 may be due more to lack of specialized collecting 

 than to absence of the beetles. Hydraena, with some- 

 what fewer subgenera and species, is dominantly Old 

 World and has much the same distribution, but is 

 better represented in Central America. Limnebius has 

 a similar distribution, but apparently did not reach 

 Australia or South America. 



Taxonomic characters. — In Ochthebius and Hydraena 

 the form and sculpture of the pronotum and elytra offer 

 readily seen differences; in the former, the shape of 

 the labrum; in the latter the legs often show sexual 



dimorphism. In Limnebius the dorsal sculpture and 

 body form have been used. The male genitalia show 

 specific differences in all three genera. 



Key to Nearctle Genera of Hydraenidae 

 Adults 



1. Second segment of hind tarsi elongate, longer than the 

 3rd segment; pronotum as broad basally as base of 

 elytra, smooth, not coarsely punctate or sculptured, 

 sides evenly arcuate; black or rufescent beetles, about 

 1 mm. long. LIMNEBIINAE Limnebius Leach 1815 



— Second segment of hind tarsi short, about as long as 

 3rd; pronotum at base slightly or decidedly narrower 

 than base of elytra, surface uneven, coarsely punctate 

 or with a transparent lateral boarder, sides sinuate 

 or irregular; black, reddish, or aenescent beetles, 

 1 to 2 mm. long. HYDRAENINAE 2 



2. Maxillary palpi very long, much longer than antennae; 

 pronotum coarsely, closely punctate, sides without a 

 transparent border (fig. 13:25c) 



Hydraena Kugelann 1 794 



— Maxillary palpi shorter than antennae; pronotum vari- 

 ously sculptured, often with deep fossae and grooves, 

 almost always with a transparent border in at least 

 basal half (fig. 13:25d) Ochthebius Leaoh 1815 



Key to Nearctle Genera of Hydraenidae 

 Larvae 



1. Setae on clypeus not placed at anterior margin and 2 

 median ones distant from each other; lacinia mobilis 

 narrower (fig. 13:26c); inner lobe of maxillae not dis- 

 tinctly divided apically, cerci nearly contiguous proxi- 

 mally and divergent (fig. 13:28c) 



Ochthebius Leach 1815 



— Setae on clypeus placed at anterior margin and equi- 

 distant; lacinia mobilis "broader; inner maxillary lobe 

 distinctly divided apically; cerci widely separated 

 proximally and nearly parallel 2 



2. Third antennal segment without inner swellings, 

 segment 2 with a single antennal appendage; a pair 

 of pectinate setae at anterior margin of labrum (fig. 

 13:286, d) Hydraena Kugelann 1794 



— Third antennal segment with an inner swelling; 2nd 

 with 2 slender antennal appendages; no pectinate 

 setae at anterior labral margin; inner maxillary lobe 

 strongly divided (fig. 13:28a) 



Limnebius Leach 1815 



Key to California Species of Limnebius 

 Adults 



1. Dorsal surface more or less polished; California 



piceus (Horn) 1872 



— Dorsal surface more or less alutaceous 2 



2. Elytral base slightly narrower than prothorax; pronotum 



and elytra strongly alutaceous; California 



alutaceus (Casey) 1 886 



— Elytral base equal in width to prothorax; pronotum and 

 elytra only feebly alutaceous; California 



congener (Casey) 1 886 



Genus Hydraena Kugelann 



H. vennsylvanica Kiesenwetter used to be credited to 

 the Pacific Coast, but California specimens were 

 later separated and described as H. vandykei d'Orchy- 

 mont. 



