117 



abdomen in the latter is so very clifFcrent, besides tlieir having but one 

 recun-ent nervure, their differently formed head, mandibles, and palpi 

 &c. present characters which it would be incongruous to associate to- 

 gether, and I presume Latreille united thein because he knew but the 

 single genus Aulacus, in which, it is true, some points of structure 

 apparently agreed, but wherein there were certainly more, and more 

 peculiar ones, that disagreed ; but I expect he was unwilling to con- 

 struct a family of a single genus. 



Having thus given my reasons for what I am about to do, I will 

 proceed to the matter in hand, namely, in the first place, to some col- 

 lateral affinities. 



Family. — Evaniad.e, as restricted by Shuckard. 



Abdomen usually inserted closely to the scutelkim and compressed, 

 and springing abruptly from the surface of the metathorax. Superior 

 wings with either a closed first submarginal cell, which receives the 

 single recurrent nervure, or without any, but some of the ordinary 

 basal nervures. 



Superior wings with 



a complete marginal and submarginal cell : 



abdomen attached by means of an abrupt petiole. 1. Evania. 



abdomen increasing gradually from its insertion. 4. Fcenus. 

 neither marginal nor submarginal cells : 



basal cells completely enclosed 2. Brachygaster. 



basal cells unenclosed 3. Hyptiam. 



The preceding genera constitute, according to my views, all that 

 truly pertain, as far as I know the Hymenoptera, to tlic Evaniadiv, 

 which, fi-om the mode of attachment of the abdomen, forms so pecu- 

 liar and insulated a group in the Hymenoptera. 



The careful investigation of affinities, in obscure groups, being a 

 subject always replete with interest, and the most instructive perhaj)s 

 in the study of the natural sciences, as it necessarily involves an inti- 

 mate and comprehensive knowledge of structure ; I shall make no 

 apology for incidentally introducing here my views as to the true po- 

 sition of Mr. Westwood's genus, Megalyra, included by that Ento- 

 mologist, together with Aulacus and Pelecinus, in the family Evaniadaj, 

 but from which it is as distinct, and especially from the latter, as are 

 Stephanus and Paxylomma. 



We invariably see that where nature leaves one normal type of form 

 to assume another distinct one, in her struggle to divest herself of the 

 old relations, new, abnormal, and insulated forms are generated, and 



