37-4 IIYMENOPTERA OF AMERICA. [PART I. 



very slightly pediculate (or even triangular), terminating toward 

 the radial in a point or a subpediculate point, which constitutes 

 an insensible passage to the Odynerus. So the Odynerus Alas- 



ioroides might figure indifferently in the one or the other of the 

 two genera. 



The Alastor is met with on all the continents, but it is rare 

 or in all eases very much loss numerous than the Odynerus. It 

 is in Australia that it attains its maximum development, and in 

 that region of our globe it appears almost to balance the Odym rus 

 by the number of its species. In Europe but one species is 

 known. America furnishes a small number of species, but doubt- 

 less more will yet be collected. It is probable that the United 

 States possess their Alastor as well as Europe, although it has 

 not yet been met with. 



The species of the new continent form a peculiar type with a 

 form lengthened and cylindrical, recalling the Stenodynerus and 

 the Stenancistrocerus, but with the peculiar characteristic of 

 having the metathorax notably prolonged beyond the post-scutel, 

 and then abruptly truncate, and offering a circular concavity, 

 bordered bv a rid^e, verv trenchant and of a circular form. 



'D 



Subgenus ALASTOROIDES. 



(Sadss. Vespides. Ill, 327.) 



First abdominal segment parted by a transverse suture. 



The American species form the 



Division HYPALASTOROIDES. 

 CSauss. Vespides, III, 328.) 



Metathorax superiorly produced behind the post-scutel ; then 

 truncate. Its margins sharp. 



1. A. TllexicailUS Sauss. — Gracilis, niger. crasse punctatns ; pronoto 

 lato. biangulato ; met.moto valde rugoso, pone post-scuiellum producto, 

 postice valde foveolato ; foveola? marginil>us superne semicirculariter 

 areuatis, acutissimis, denticulatis, niarginibns inferis borizontaliter in 

 laniellam bilobatam prodnctis; abdornine basi acute truncato; pronoti 

 et abd. segmentornm l l , 2' margine, Pcntelli margine interrupto, 

 metanoti cantbis iuferis, fasciaque tibiarum, flavis ; alis nebulosis 



