HYMENOPTEROUS PARASITES. 277 



tapered from middle toward base and apex, more strongly so behind; 

 base medially with some short fine longitudinal striee and toward each 

 side with a larger and deeply impressed groove that extends to the 

 basal fourth; third segment one-third as long as the second, very 

 narrow and evenly contracted to the more or less blunt apex; fourth, 

 fifth and sixth segments tubular capable of being entirely retracted; 

 the fourth nearly as wide as the tip of the third, but the other two very 

 slender; ovipositor never extending much beyond the sixth segment. 

 In the most fully extruded example the fourth to sixth segments 

 together measure 1.5 mm., or distinctly more than the length of the 

 remainder of the abdomen. Wings absolutely hyaline, without dis- 

 tinct marginal fringe, except for some almost transparent hairs api- 

 cally; disc bare. Hind wing with two delicate frenulum hooks. 



Type and eight paratype specimens from Kartabo, British Guiana 

 (W. M. Wheeler). 



This species is represented by fewer specimens in the collection than 

 any of the others. 



Isostasius crassus sp. nov. 



9 . Length 1.0 mm. Black; coxae piceous, the trochanters, base 

 of femora and tibiae and tarsi, except last joint pale yellowish; re- 

 mainder of legs dark brown or piceous. Wings hyaline, the vein 

 fuscous. Head considerably broader than the thorax, flattened, more 

 than twice as wide as long when seen from above. Ocelli large, close 

 together, the lateral ones as far from the eye-margin as from the median 

 one; vertex and occiput shagreened, subshining; face shagreened, 

 but more shining; lower margin of face elevated at the insertion of the 

 antennae; makir space indistinctly transversely striated, more than 

 half as long as the width of the nearly round eyes; head behind eyes 

 shagreened, with a faint trace of striae curving upwards across the 

 cheeks. Antennae 10-jointed, less than half as long as the remaining 

 joints together, rather stout, more slender basally; pedicel large, 

 almost as broad as the scape, one-half longer than wide; funicle, con- 

 sisting of the first four flagellar joints, short, the joints very small, of 

 about equal length and quadrate, except for the broader and dis- 

 tinctly transverse fourth joint, club large, first joint narrower than the 

 others; second and third very broad, nearly twice as wide as long, last 

 elongate, triangular, narrower than the preceding one. Thorax broad, 

 the mesonotum as broad as long and the pleurae only slightly visible 

 from above; mesonotum shagreened; rather dull, sparsely clothed 



