ODYNERUS. 353 



tibiisque basi, flavis. — %. Clypeo flavo-bidentato ; antennaiuni soapo 

 subtus fla'- T o. 



Odyn. Acolhuus Sauss. Revue de Zool. IX, 1857, 280. 



Total length, 7 mm. ; wing, 5 ram. 



Very small. Head circular or slightly wider than long, rather 

 thick, emarginate behind. Sinus of the eyes not much opened 

 on the inner side Thorax wide anteriorly; prothorax having 

 its anterior margin a little concave, crested, its angles spiniform 

 or at least sharply angulate. Scutel flat above, vertically trun- 

 cate ; the truncation making a hinder face, transverse, a little 

 rounded on the lateral angles ; the sharp edge separatino- the 

 superior and posterior face quite crested; the crest erect, trans- 

 verse, very finely r crenulate (sometimes not well developed). 

 Metathorax rounded-triangular, a little prolonged backward, 

 convex, parted by a groove or a channel. Its apex with pro- 

 duced bifid articulate valves, but not spined. Head and thorax 

 densely punctate, the metathorax more finely punctate than the 

 rest, silky; the lateral ridges garnished with argenteous hair. 

 Abdomen elongate, fusiform (spindle-shaped), subpetiolate ; the 

 first segment longer than wide; its base shortly petiolate, the 

 remainder funnel-shaped, swelled above, a little toothed on each 

 side; sometimes transversely channelled before the edge. Second 

 segment not much elongate, bell-shaped, a little depressed. First 

 segment cribrose like the thorax ; 2d more finely punctured, 

 except on its hinder margin ; 3d and following segments not 

 sensibly punctured. 



Black. Head quite black; orbits silvery; a yellow spot at 

 base of the scape. Anterior margin of prothorax, a spot under 

 the wing, posterior margin of scutel, articular valvar of meta- 

 thorax, and the margin of the first two abdominal segments, 

 yellow. Tegulas ferruginous. Feet black; tibiae maculate with 

 yellow at base; their apical spine yellow. Wings smoky, prin- 

 cipally on the anterior margin. 



Var. a Segments 3-5 margined with fuscous. 



b. Fascia of scutel wide or narrow. 



c. Segments 4, or 4 and 5 incompletely marginate with yellow. 

 9. Clypeus ovate-circular, black, punctate, rather bidentate. 



% . Clypeus yellow, nearly heart-shaped, but reversed; the 

 inferior part widest, with a little notch in the middle, forming 

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