70 U. S. NATIONAL MUSEUM BULLETIN 2 1 6 part a 



3. Genus Gambrus 



Figure 309,b 



Kaltenhachia Foerster, 1868, Verb. Naturh. Ver. Rheinlande, vol. 25, p. 187. 



Type: {Cryptus ornaius Grsbvenhorst) =incubUor (Linnaeus); designated 



by Viereck, 1914. 

 Gambrus Foerster, 1868, Verb. Naturh. Ver. Rheinlande, vol. 25, p. 188. Type: 



Gambrus maculatus Brischke; included by Brischke, 1888. 

 Hygrocryptus Thomson, 1873, Opuscula entomologica, fasc. 5, p. 513. Type: 



Cryptus carnifex Gravenhorst; designated by Viereck, 1914. 

 Allocryptus Viereck, 1917, Bull. Connecticut Geol. Nat. Hist. Survey, voL 22, p. 



333. Type: (Agrothereutes (Allocryptus) hyslopi Yiereck) =ultimus (Cres- 



son) ; monobasic. 



Front wing 2.8 to 9.8 mm. long; flagellum of male sometimes with 

 a pale median band or stripe; clypeus of moderate size, moderatel}^ 

 convex, its apical margin convex, usually with a more or less distinct 

 median apical lobe or blunt tooth; mesoscutum mat and with moderate 

 sized or fine punctures; apical carina of propodeum complete, its 

 median portion more or less bowed forward, its sublateral portion 

 often forming a weak crest; areolet always subquadrate; ovipositor 

 sheath 0.35 to 0.9 as long as front wing. Agrees otherwise with the 

 generic description of Agrothereutes. 



Gambrus is closely related to Agrothereutes, from which in our 

 area it may be distinguished by the characters in the key. In Em-asia, 

 however, are some apparently intermediate species and there the 

 two genera cannot be satisfactorily separated. The distinction be- 

 tween Gambrus and Aritranis is also somewhat arbitrary, but easier 

 and more natural than that between Gambrus and Agrothereutes. 

 There are nine Nearctic species, and in Eurasia probably a larger 

 number. 



Keys to the Nearctic species of Gambrus 



MALES 



1. Femora entirely or largely black or fuscous 2 



Femora entirely or mostl}' ferruginous 3 



2. Tergites 2-4 ferruginous, sparsely punctate ... 3. tunicularubra (Fyles) 

 Tergites 2-4 black, densely punctate 1. bituminosus (Cushman) 



3. Middle coxa partly or entirely whitish or stramineous; flagellum nearly always 



with a median white stripe above 4 



Middle coxa black or ferruginous; flagellum entirely blackish 6 



4. Seventh tergite with a median apical white spot; hind basitarsus entirely 



white, or rarely a little infuscate 7. nuncius (Say) 



Seventh tergite entirely black; hind basitarsus largely or entirely fuscous, 

 rarely entirely white 5 



5. Subapical tyloids narrow and sharp 8. extrematis (Cresson) 



Subapical tyloids wide, about 0.28 as wide as their segments. 



9. polyphemi Townes 



