Vol. XXV] ENTOMOLOGICAL NEWS I/ 



TERGITES There are two principal plates found in the ter- 

 gal region of winged insects. These are the scutoscutellwm, 

 or large anterior plate Scsl (Fig. 2), and the postscutellum, 

 or smaller posterior plate Psl. The scutoscutellum bears the 

 wing, or the wing articulates with its lateral margin. The 

 postscutellum is not connected with the wing in any insects 

 thus far observed. In some insects the scutoscutellum is con- 

 nected with the pleural region by a pre-alar bridge, or con- 

 necting sclerite Pal (Figs. 2 and 5), extending in front of the 

 wing; while the postscutellum is usually connected with the 

 pleural region by a post-alar bridge Plph (Fig. 2), extending 

 behind the wing. 



There frequently occur "implexes" (i. e., any in-folding, or 

 in-pocketing of the integument) which serve the double pur- 

 pose of affording better attachment for the muscles, and of 

 strengthening, or rendering more rigid, the sclerites in which 

 they occur. The outward manifestation of such an "implex," 

 or internal fold, is an external groove or suture, formed by 

 the meeting of the external lips of the fold. Naturally, these 

 folds, or plaits, are composed of two plates. These may be 

 so closely applied to each other as to appear as a single plate. 

 Both plates may be equally strongly chitinized, or one may be 

 strongly chitinized and the other membranous. 



The transverse "implexes" of the tergal region are termed 

 phragmas, and these occur at the dividing line between two 

 consecutive segments, so that the anterior plate of the 

 phragma may be considered to belong to the segment in front, 

 and the posterior one to the segment behind. If the anterior 

 plate of the two which make the phragma is strongly chitiniz- 

 ed while the other is membranous, the phragma appears to be- 

 long entirely to the segment in front. If the posterior one is 

 strongly chitinized, while the other is membranous, the 

 phragma appears to belong to the segment behind. The an- 

 terior plate of the tergal region (i. e., the scutoscutellum, men- 

 tioned above) may bear a phragma at its anterior margin, or 

 the posterior tergal plate (i. e., the postscutellum) may bear 

 a phragma along its posterior margin. 



The anterior tergal plate Scsl (Fig. 2) may be further di- 



