278 BRUES. 



with fine appressed hairs hke the remainder of the thorax and the head; 

 parapsidal furrows deHcate, quite distinct behind, but obsolete in 

 front. Seutellum strongly convex medially, noticeably elevated above 

 the level of the mesonotum, separated at the base by a narrow impres- 

 sion, wider at the sides; posterior margin defined by a semicircular 

 raised margin inside of which is a deep submarginal groove. Propo- 

 deum trilobed behind, woolly on the sides and with a pair of longi- 

 tudinal ridges on its central portion. Abdomen short, ovate, barely 

 longer than the thorax; first segment short, more than twice as broad 

 as long, slightly woolly and longitudinally fluted; second segment 

 shining, very convex, twice as long as wide, broadest at the middle, 

 and forming the entire gaster except for the small, elongate-triangular 

 third segment; second finely longitudinally striate at its extreme base, 

 with a larger and deeper groove at each side of the base; third segment 

 punctulate, with sparse pale hairs. Venter highly convex, the lateral 

 carina not very distinct. Propleurse shagreened; mesopleura broadly 

 impressed medially and behind, obliquely striate near its posterior 

 border; metapleura thinly clothed with short pale hairs. Ovipositor 

 only slightly projecting, curved downwards. Legs rather slender, the 

 femora strongly clavate, the tibiae more weakly so. Wing with a short, 

 but distinct marginal fringe, the disc bearing strong and rather large 

 hairs except at the base; vein capitate, one-third as long as the wing. 



Type and 12 paratype specimens from Kartabo, British Guiana 

 (W. M. Wheeler). 



As may be gleaned from the taxonomic description (p. 270) of Gastro- 

 trypes, both species have the abdomen lengthened as in Dolichotrypes, 

 but the stylate fifth segment is not of variable length so that, exclusive 

 of the greatly elongated apical membranous segments, all individuals 

 are of approximately equal length. The membranous parts may be 

 entirely retracted or extruded to a length equalling that of the entire 

 remainder of the abdomen. 



Similarly in Platygaster tubulosa the apical abdominal segments (in 

 this ?ase the fourth and following) are tubular and capable of complete 

 retraction or of extrusion to a length somewhat greater than the re- 

 mainder of the abdomen. 



The foregoing observations on Dolichotrypes and the Gastrotrypes 

 and Platygaster associated with it in British Guiana, suggested an 

 examination of several other Serphoid Hymenoptera. A brief account 

 of these is given below. 



A similar elongation of the terminal portion of the abdomen occurs 

 in females of members of the genus Serphus (Proctotrypes), but here the 



