PROC. ENT. SOC. WASH., VOL. 24, NO. 1, JAN., 1922 21 



ABDOMEN. Only five abdominal segments are visible 

 ventrally (S3-S7, fig. 17), while seven are visible dorsally 

 (T1-T7, fig. 22). The first apparent ventral segment is there- 

 fore morphologically the third or the fused second and third. 

 Sometimes anywhere from one to three additional segments 

 are partially visible, but these form a protrusible carrier for 

 the external genitalia and are not ordinarily visible in dry 

 specimens. The outline of the abdomen is elongate triangular 

 with the sides gently arcuate, especially on the apical third. 

 The following descriptions of the abdomen are from communis 

 Gyll., but are applicable in general in every species the writer 

 has examined 



The first six tergites (T1-T6, fig. 22) are membranous and 

 hardly distinguishable from the tergo-pleural membrane. The 

 median length of the first tergite is slightly less than that of the 

 second, and the two together are about as long as each of the 

 following five. The seventh tergite (T7, figs. 22 & 23) is similar 

 in both sexes; it is slightly narrower than the preceding segment, 

 slightly longer, and is moderately chitinized and flexible. Its 

 outline is roughly parabolic; it is fimbriate posteriorly and 

 broadly rounded medianly; emarginate on either side before 

 the apex, with a longitudinal impression beginning at the 

 emargination and continuing more or less parallel with the 

 lateral margin nearly to the base. 



The tergum of the abdomen is bordered on either side by a 

 sharp lateral ridge (LR, fig. 22) extending from the second to 

 about midway of the seventh tergite. It is formed by the 

 pleura. A gutter-like channel into which the edge of the 

 elytron fits, separates it from the sternites. 



Borne on the tergo-pleural membrane, and therefore visible 

 only dorsally, are seven pairs of spiracles, each marking a 

 urosegment (Spl-Sp7, fig. 22). The first spiracle (Spl, figs. 

 14 & 22) is wide and soft-lipped and deeply set in the membrane; 

 it is suboblong, extends along the entire length of the oblique 

 lateral margin of the first tergite and is arcuate on its anterior 

 fourth. The second spiracle is slightly elongate-oval, some- 

 what obliquely placed and is about one-fifth the length of the 

 first; it is located in a deep fold of the membrane about one- 

 third of a millimeter from the lateral ridge. The stoma of this 

 and the succeeding spiracles is somewhat chitinized. The 

 third to seventh spiracles are slightly smaller and rounder and 

 are located a little nearer the lateral ridge. 



The sternites of the abdomen (S3-S7, fig. 17) are heavily 

 chitinized and strongly convex. The posterior angles of 

 sternites 4, 5 and 6 are somewhat produced, the prolongation 

 becoming more pronounced preceding posteriorly. The last 

 visible sternite is subtriangular, its sides arcuate and its apex 

 acutely rounded, \nfissilis Say the median length of the first 



