122 GENERA OF IIYMKXOl'TERA. 



Last dorsal segment of abdomen 9 ''road, flat, triangular, the sides 

 straight, not recurved ; % antcinue with middle joints often more 

 or less dilated, tlie anterior tibiie witli a sliield-like expansion. 



Tli.vi-eopii!^ St. Farg. 

 Second discoidal cell long, narrow, obtusely pointed at apex, longer than 

 the first discoidal cell, which is irregular in shape, receiving the dis- 

 coidal iiervure about one-third from the base, the submarginal cell 

 receiving the recurrent nervure at about the middle ; abdnnitii ses- 

 sile, venter flat; form short, robust Aiiaci'abro Pack. 



Eyes hairy ; maiidibles emarginate exteriorly. .Eiitoiuogiialliii!i» Dahlb. 



Submarginal cell confluent with the first discoidal cell, only separated from it 



liy a very indistinct nervure; postscutellum with a membranous 



wing-like appendage on each side ; metathorax with a curved spine 



near the base Oxybelli^t Latr. 



The geuus Trypoxylon i.s readily recognized by the reniform eyes 

 and long clavate abdomen, and is the only genus in the family 

 where the neuration of the posterior wings is complete. The number 

 of described species is few, and not unconniion. 



Rhopalmn has the abdomen petiolate, with the apex of the first 

 segment nodiform ; the species are of small size, and only two have 

 been described. 



Crabro has numerous species, varying in size from moderately 

 large to quite small, and which have been divided into many sub- 

 genera, the characters founded chiefly on the armature of the legs ; 

 among these is Blepharlpas, to which several North American s^jccies 

 have been referred ; these are all of small size, with subpetiolate ab- 

 domen, and with a single exception, have the abdomen entirely black. 

 Thyreojms has generally been ranked among the subgenera, and 

 doubtless properly so, but it is placed in the table given above because 

 of easily recognized and tolerably constant characters. 



Anacrahro is represented by a single small, robust s])ecies, having 

 somewhat the appearance of Oxybelu>i, and at once distinguished by 

 the linear form of the second discoidal cell. 



Entomognatkus, distinguished by the hairy eyes, has, as far as 

 known, but a single representative in our fauna, and which occurs in 

 iexas. 



Oxyhelus is remarkable for the armature of the metathorax and 

 confluence of the submarginal and first discoidal cells. 



The genera and species are described at length by Packard in his 

 " Revision" previously referred to. 



