WALSH DESCRIPTIONS OF N. AM. HYMENOPTERA. 1 65 



figure, there exist in the tibia of the degraded Dipterous genus 

 Nycteribia two subequidistant transverse sutures, whether free or 

 connate does not appear. But Latreille says nothing of any 

 such character in his description of the genus, and I find no traces 

 of any sutures, whether free or connate, in the tibia of the allied 

 genus Ornithomyia. (See Westw. Intr. ii. p. 580, fig. 15, and 

 Latr. Gen. Cr. Ins. iv. p. 364.) The bullse oi Xylonomus are very 

 distinct but exceedingly minute, being stouter than the width of 

 the vein they occupy. They are three in number, C, D, and E ; 

 C and D equidistant from each other and from the tips of their 

 vein, and E much nearer the tip than the base of its vein. There 

 are no semi-bullae, such as exist in Odontomerus, probably because 

 the areolar cross-vein is here subobsolete. 



lylonomas {Acxnitus) Stlgmapterus, Say. — 5. — Black, ^«fl</ opaque 

 ■with fine, dense rugae, subopaque on the vertex. Face projecting beyond 

 the eyes J of their shorter diameter. Clypeus scarcely as long as the fla- 

 gellum of the antennae is wide. Labrum longitudinally semi-oval, with 

 rufous hairs. Mandibles unarmed. Palpi black, the last 3 joints whitish. 

 AntennSe | as long as the body, scarcely clavate at tip; the ist joint of the 

 flagellum thrice as long as wide, and 6 or 7 of the following joints \ longer 

 than the ist; a white annulus extending from the middle of the 9th to the 

 middle of the 14th joint of the flagellum. Thorax finely and closely punc- 

 tured, subpolished below, subopaque above, with 8 or 9 coarse, close-set 

 longitudinal striae at the bottom of the coUare, and some finer bi-flabellate 

 ones at the base of the middle lobe of the mesonotum. Metathorax finely 

 rugoso-punctate, coarsely on its pleura ; the carinate areas all perfect save 

 that the basal is confluent with the central area, the latter equally long with 

 the former but 2J times as wide, of a truncate-dvate shape, and J longer 

 than wide. Tip of each lateral area prolonged into a robust thorn directed 

 upwards and backwards. Mesonotum in front of the scutel (except the 

 striate space), and also the mesothoracic pleura, rufo-piceous. Abdomen 

 subopaque, with very minute, dense, shallow rugae ; coarser on the ist joint, 

 especially towards its tip. Joint i, 3^ times as long as wide, thrice as wide 

 behind as before, its sides straight except that their extreme tip is a little 

 constricted and that the spiraculiferous tubercle is placed § of the way to 

 their tip ; the two carinae indistinctly traceable to the tip, where they co- 

 alesce in a small, subpolished tubercle, thre intervening space level except 

 that there is a shallow groove opposite the spiracles. On joint 2, from the 

 tip of each carina of joint i, there proceeds an oblique, impressed stria to 

 the middle of the lateral edge so as to cut off an elongate triangle. Joint s 

 longer by ^ than wide ; 3 longer by \ than wide ; 4-7 short ; 8 rather longer 

 than wide, curved upwards and tapered to an acute point when viewed in 

 profile, truncate-triangular when viewed from above. Ovipositor piceous, 

 ^ longer than the body ; sheaths black, regularly and slowly tapered to the 



