62 BULLETIN 15, UMTED STATES NATIONAL MUSEUM. 



MESITIUS Spinola. 



Coniptc. rendu Ilyui. do Para (184H); Mom. Atad. Turiu, S^r. ii, torn 13 (1853); 



Westw., Thes. Ent. Oxoii., p. 222. 



(Type J/, ffhiliauii Spin.) 



Head oblong, subconvex, not much longer than wide; eyes oval; 

 ocelli distinct. 



Antenuiw 13-jointed, in $ long, in ? much shorter, the scape thickened, 

 about four times as long as the pedicel, the following joints short. 



Maxillary palpi rather long, 6-joiiited, the three basal Joints gradu- 

 ally increasing slightly in length, the three terminal ones longer and 

 subequal; maxilla terminates in three membraneous ciliated lobes; 

 labial palpi 3-jointed, the Joints nearly e<iual. 



Mandibles oblong, with the apex oblique and but slightly sinuated ; 

 in the 9 the outer tooth is small, acute, followed by a very small tooth, 

 the rest of the surface scarcely denticulate; in S 4- or 5-dentate. 



Thorax: Prothorax long, triangular or trapezoidal, the apex at the 

 junction with the head contracted, with a deep transverse furrow above; 

 mesonotum usually with two distinct furrows, often abbreviated poste- 

 riorly; scutellum with two fovese at base ; metathorax with prominent 

 Ijosterior angles, the dorsum with many longitudinal carinae. 



Front wings with a moderate sized stigma, a long, incomplete marginal 

 cell and two basal cells, the apices of both being more or less oblique. 



Abdomen ovate or oblong-ovate, smooth, the second segment the 

 longest, the apical margins sinuate or emarginate. 



Legs as in Epyris, the claws slender, nearly straight, with a tooth at 

 the middle. 



This genus closely resembles Epyris and great care is necessary to 

 distinguish it from that geuus. As far as the North American species 

 are concerned I have had no difficulty in separating them by the two fo vea3 

 at the base of the scutellum. 



Westwood, in Thesaurus Entomologicus Oxonieusis, p. 222, and in the 

 Transactions of the Entomological Society of London, 1881, p. 125, 

 states that the genera Isohrachium Forster (Hym. Stud., ii, p. 96, 1856) 

 and Heteroccelia Dahlbom (Hym. Europ., ii, p. 21, 1854) are synony- 

 mous with Mesitius, an opinion in which I can not concur. The apical 

 segments of the abdomen of Heteroccelia nigriventris Dahl., the type 

 of the genus, is figured by Dahlbom, loc. cit., p. 23, and it, as well as 

 the description, plainly point to a chrysidid. Dahlbom also figures it 

 on PI. 1, Fig 15. A careful comparison of this figure with Westwood's 

 (Thes., PI. 31, Fig. 10) plainly shows that Dahlbom has a genuine 

 chrysidid and Westwood a genuine proctotrypid. 



It is inexplicable to me how so careful a worker as Westwood could 

 have made so grave an error. Forster, in his definition of the genus 

 Isohrachium^ evidently confused and correlated as sexes two distinct 

 insects. His Isohrachium dichotomus is a $ , and evidently a genuine 



