302 PROCEEDINGS OF THE XATfOXAL MUSEUM. vol. xxxi 



and those here given are likely to be modified by more careful study 

 of the development of these insects. It is certain that the limits here 

 indicated are most unsatisfactory to the writer. As in the mesothorax 

 no dividing line between the pleuron and sternum is visible, and the 

 latter plate has no distinctive features of value. 



Ahdomen. — The median segment or propodeum is really the first 

 segment of the abdomen, which has assumed close connection with the 

 thorax and has often been considered as one of the segments of that 

 division. It is follow^ed b}^ a remarkably slender, constricted portion 

 of the second abdominal segment, termed the petiole, at the hinder end 

 of which the plates of the segment suddenly enlarge to average size. 

 The first segment of the abdomen then is closel}" joined to the thorax 

 and separated from the greater part of the abdomen by the constricted 

 petiolar part of the second segment. This misleading appearance 

 should be kept in mind in any morphological considerations, but as a 

 matter of convenience in this paper the petiole together with its 

 enlarged posterior end is counted as the first abdominal segment. 



The median segment lies between the metathorax and the petiole, and 

 is more or less completel}^ fused with the former. Its dorsal surface 

 or dorsum lies immediate!}' posterior to the postscutellum and extends 

 backward more or less horizontally for some distance to where the 

 outline of the bod}^ bends ventrally toward the petiole. At this point 

 there is a depression or fovea of the chitin on the median line, which 

 varies in outline in different species. In some cases it is decidedly 

 crescentic, the concavity of the crescent being dorsal, wbile in other 

 cases it is nearly circular in outline. The depth of the fovea also 

 varies, being much greater in some cases than in others. On each side 

 of the median segment, nearly on the line of the attachment of the 

 wings and about halfway from the front to the rear of the dorsum is a 

 stigma — the stigma of the median segment. A more or less well -devel- 

 oped line joins the upper end of the stigma with the fovea on the one 

 hand and with the side of the anterior edge of the dorsum at the post- 

 scutellum on the other, these lines taken together limiting the dorsum 

 and giving to it a somewhat shield-shaped outline when viewed from 

 above, the form varying somewhat in different species according as 

 the direction of these lines varies. 



In many of the Chlorioninie a groove extends forward from the side 

 of the petiole, passing a short distance above the base of the metacoxa, 

 where it is interrupted by a small swelling serving to check too great 

 an upward movement of the coxa, and curving upward till it unites 

 with the ventral end of the stigma of the median segment. This groove 

 is known as the stigmatal groove. The portion of the median segment 

 between the fovea and the petiole, and extending as far to each side 

 as this groove, may for convenience be designated as the posterior end 

 of the segment. (Plate VI, fig. 1.) 



