208 NORTH AMERICAN SCELIPHRON (hYMENOPTERA) 



fits into an emargination on tiie lower margins of tfie clypeal and 

 genal extensions wfien the mandible is closed, but swings inwards 

 leaving the emargination empty when the mandibles are open. 



Antennae. — The antennae are situated in the middle of the 

 frontal area and articulate in two oval sockets facing obliquely 

 outwards, thus giving the antennae a wide range. They are of 

 medium length, consisting of twelve segments in the female and 

 thirteen in the male. 



The proximal segment, or scape, is divided into a small basal 

 portion, the bulb, which articulates with the head in an oval 

 socket, and a larger part, the scape proper. The latter is to all 

 appearances a separate segment from the bulb, but the two parts 

 are generally regarded as one segment. The true scape is some- 

 what oval and enlarges suddenly after its junction with the bulb, 

 forming the thickest part of the antenna. The second segment, 

 or pedicel is small, rounded proximally where it articulates with 

 the scape and truncate distally where it joins the first segment 

 of the filament. The remaining segments constitute the flagel- 

 lum or filament and are more or less cylindrical. All the seg- 

 ments of the flagellum, except the last, are smaller at their proxi- 

 mal ends, the first being noticeably so. The first three segments 

 are of about the same length and either the first or second may be 

 the longest according to the species. The remaining segments 

 gradually decrease in length to the penultimate, which is the 

 shortest. The last segment is slightly longer again and tapers 

 distally to a more or less truncate end. 



The antennae are dark in color, the scape and pedicel being 

 either dark blue or dark green with strong hairs on the inner side, 

 while the flagellum is dull black, but the covering of fine recum- 

 bent hairs may give it a greyish appearance. 



Thorax 

 Prothorax. — The prothorax falls naturally into two parts, a 

 somewhat narrow anterior portion articulating with the head and 

 known as the neck, and a broader part behind, which articulates 

 with the mesothorax and is usually termed the collar. Seen from 

 above the neck is flatly convex, narrow in front and widening 

 posteriorly to the collar, and the angle of inclination of these 

 dorsal surfaces to each other varies, being sometimes acute and 



