374 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 cases very much less 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 Odynerits 

 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-scute], 

 and then abruptly truncate, and offering a circular concavity, 

 bordered by a ridge, very trenchant and of a circular form. 



Subgenus ALASTOROIDES. 



(Sadss. Vespide.s, III, 3-7.) 



First abdominal segment parted by a transverse suture. 



The American species form the 



Division IIYPALASTOROIDES. 

 £Sauss. Vespide.s, III, 328.) 



Metathorax superiorly produced behind the post-scutel ; then 

 truncate. Its margins sharp. 



1. A. Wlexicamis Sadss. — Gracilis, niger. crasse punctatus ; pronoto 

 lato, biangulato ; metanoto valde rugoso, pone post-scutellum produoto, 

 postice valde foveolato ; foveolae marginibus superne semicirculariter 

 arcuatis, acutissimis, denticulatis, marginibus inferia horizontaliter in 

 tarn ell am bilobatam prodnctis; abdomine basi acute truncato; pronoti 

 et abd. segmentorum 1', 2' margine, scutelli margine interrupto, 

 naetanoti canthis inferis, fasciaque tibiarum, flavis ; alia nebulosia 



