MONOGRAPH OF THE NORTH AMERICAN TROCTOTRYPID.E. 223 



ments tlie longest, about equal in lengtli; fourth, the length of the 

 first; fifth, two-thirds the length of the fourth; sixth, half the length 

 of fifth; seventh very sliort, smooth basally; eighth subtriangular, 

 margined. Antennae filiform, dark brown, the scape and pedicel yellow ; 

 second, third, and the last joint of flagellum about equal in length; 

 first and fourth about equal, shorter than the second; joints beyond 

 very slightly shorter. Wings hyaline, Mith a large smoky blotch below 

 the postmargiual vein; nervures fuscous; basal nervure distinct; mar- 

 ginal nervure as long as the shaft of the stigmal, the latter oblique, 

 clavate at tip. 



Habitat. — St. Vincent, West Indies, 



Types in National Museum and British Museum. 



Described from 4 6 specimens collected by Herbert H. Smith. 

 CACUS, geu. nov. Riley. 

 (Typo C. acanthi Riley.) 



" Head subquadrate, emarginate behind, the occiput feebly margined ; 

 ocelli 3, triangularly arranged, the lateral close to the eye; eyes ovate, 

 bare. 



"AntenntTe inserted at tlie clypeus, 12-jointed in both sexes; in $ cla- 

 vate, the club G-joiuted, the last funicular joint usually transverse, the 

 others longer than^wide; in $ filiform, the third funicular joint a little 

 dilated and emarginate toward base. 



"Mandibles short, either tridentate or bifid at tip. 



"Maxillary palpi 3-jointed; labial palpi 2-jointed. 



"Thorax ovate, narrowed before, the prothorax slightly visible from 

 above; mesonotum most frequently without furrows, rarely Avith dis- 

 tinct furrows; metathorax not especially short, with two lateral keels, 

 a median prominence or carina, and with usually two small erect teeth 

 at apex, above the insertion of the abdomen, 



"Front wings with the submarginal vein joining the costa a little be- 

 yond the middle of the. wing, the marginal vein variable, scarcely half 

 the lengtli of the stigmal, or much longer; the latter oblique, termi- 

 nating in a knob; the postmargiual vein very long, the basal vein sub- 

 obsolete. 



"Abdomen much as in Barycouus, but the female M'ithout the horn- 

 like projection at base. 



"Legs as in Baryconufi, the tibial spurs 1, 1, 1, the middle and hind 

 pairs weak, tarsi long and slender, the basal joint more than four times 

 the length of the second." — [From Iiilcy\'i MS.] 



It is probable that under this genus Dr. Eiley has included two distinct 

 genera, one distinguished by having 3 dentate mandibles, the other in 

 having the mandibles bifid or 2-dentate, but otherwise they are so 

 similar that for the present I believe it best to follow him in consider- 



