306 Mr. F. Smith's Descriptions 



cence; the tips of the mandibles, and the three basal 

 joints of the antennae, ferruginous. Thorax : the posterior 

 margin of the collar and of the scutellum, the post-scu- 

 tellum and the m eta thorax, with golden pubescence; the 

 anterior coxas with golden pubescence in front; the sides 

 of the thorax obliquely striate beneath the wings; the 

 metathorax with a longitudinal central channel, most 

 deeply impressed towards the apex; the legs obscurely 

 ferruginous, the anterior pair brightest ; the wings hya- 

 line, with the anterior margin of the superior pair fuscous. 

 Abdomen : the petiole deeply channelled above, and also 

 at the sides; the channel above with golden pubescence, 

 the apical margin of the club as well as the apical margins 

 of the other segments bordered with golden pubescence; 

 beneath, smooth and shining, with the margins of the 

 segments rufo-piceous. 



Hah. — Brazil. 



In F. Smith's collection. 



This insect has the general aspect of a species of the 

 genus Polybia belonging to the Vespidce. 



Fam. NYSSONID^. 



Genus Acanthostethus, n. g. 



Head scarcely as wide as the thorax ; eyes lateral, large 

 and ovate; ocelli placed in a curve on the vertex, the 

 posterior pair in a line with the summit of the eyes; 

 antennas approximate at the base, inserted at the base of 

 the clypeus; the scape obconic, the second joint sub- 

 globose, the flagellum slightly increasing in thickness 

 towards the apex ; the clypeus transverse, its anterior 

 margin nearly straight, its lateral angles sub-dentate; 

 mandibles arcuate, edentate, and acute at their apex ; the 

 labrum concealed, transverse. Thorax ovate; the collar 

 transverse; the scutellum subquadrate; the metathorax 

 having on each side at its posterior extremity a stout 

 acute spine; superior wings ivith one marginal and two 

 complete suhmarginal cells ; the marginal cell elongate, ex- 

 tending more than half-iuay towards the extremity of the 

 wing ; the first suhmarginal longer than the marginal, and 

 more than twice the length of the second suhmarginal cell, 

 which is triangular ; the first recurrent nervure entering the 

 first suhmarginal cell towards its apex, the second recurrent 



