66 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



Ehlnoplus FoERSTBE, Verb. Naturh. ver preuss. Rheinl., vol. 19, 1862, p. 258. 



Stenospilus Foerstee, Verh. Naturh. vcr preuss. Rheinl., vol. 19, 1862, p. 259=iOplus. 



Stiropius Cameron, Journ. Roy. Agri. and Com. Soc. British Guiana, 1911, p. 329. 



Sulydus BuYssoN, Ann. Soc. Ent. Fr., 1897, p. 354. 



Thcrobolus Foerster, Verh. Naturh. ver preuss. Rheinl., vol. 19, 1862, p. 260=Opius. 



Trichopius Thomson, Opus. Ent., 1895, p. 2176=Opius. 



Trigonospilus Ashmead, Proc. U. S. Nat. Mus., vol. 23, 1901, p. 134=?Opius. 



Utetes Foerster, Verh. Natxirh. ver preuss. Rheinl., vol. 19, 1862, p. 261=Opius. 



Zetetes Foerster, Verh. Naturh. ver preuss. Rheinl., vol. 19, 1862, p. 258=Opius. 



The treatment of the genera as given here does not differ radically 

 from that by Szepligeti except that the genera Biosteres and Diach- 

 asma are combined with Ofius. After a careful study of all the 

 available material, including a number of European species, the 

 writer is convinced that it is impossible to point out any character 

 or group of characters that will always separate these groups. The 

 extremes of the genus Opius as thus constituted appear at first 

 glance to be quite different insects, but there is such a perfect grada- 

 tion and duplication of characters from one type to the other that I 

 am compelled to believe that they should constitute but one genus. 

 The name Biosteres has been shown by Viereck ^ to be isogenotypic 

 with Opius Wesmael, and to attempt to retain the old grouping would 

 necessitate changing the generic names of the majority of described 

 Opiinae. 



Stiropius is a genus described by Cameron from South America 

 since the publication of Szepligeti's monograph. 



Giardinaia, described by De Stef ani Perez, is too insufficiently char- 

 acterized to permit of its being placed in the key. It may or may 

 not be an Opiine. 



DiascTiasmimorpha Viereck, described from India, can not be dis- 

 tinguished from Opius as here defined. 



Trigonospilus Ashmead, the type of which has not been located, is 

 believed also to be an Opius. 



Key to the genera. 



1. Occiput completely margined; radial nerviire effaced before attaining the wing 



margin ; body rugulosely sculptured Ademon HaUday . 



Occipital carina incomplete; radial neivure attaining the ^\•ing margin; body 

 usually smooth and polished 2. 



2. Suturiform articulation deep, foveolate, and strongly arched, the convexity of the 



arch toward the apex of the abdomen; third tergite with an oblique furrow from 



the anterior middle to the lateral margins Gnamptodon Haliday. 



Suturiform articulation obsolete, or if defined, then straight, shallow, and not 

 foveolate; third tergite without oblique furrows 3. 



3. Clypeus three-toothed Sulydus Du Buysson. 



Clj'peua not three-toothed 4. 



4. Clypeus with a stout horn Rhinoplus Foerster. 



Clypeus without a horn 5. 



1 Bull. S3, U. S. Nat. Mus., 1914, p. 21. 



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