114 PROCEEDINGS OF THE XATfOXAL MUSEUM. vol.46. 



Color of Somatochlora semicircularis, male, field No. 4. 



Vertex metallic blue, finely and evenly punctate, evenly covered 

 with yellow pile. Lateral ocelli yellow, central ocellus brown. 

 Frons metallic blue, but with slightly more greenish tinge than vertex; 

 each lateral face of frons with yellow triangle.^ Antennae black. 

 Clypeus with center very pale yellow; wings of clypeus black; pile 

 on lower edge yellow. Labrum black. Labium very pale yellow, 

 coarsely punctate; pile white. Eyes brown above and gi'a}^ below. 

 Rear of head black, with submarginal row of white hairs. 



Prothorax black, with anterior edge of dorsum white, and a dia- 

 mond-shaped white ''cushion" at posterior edge; this "cushion" 

 covered with long white pile. Coxas white on external surface, black 

 on internal surface; legs black. 



General color of mesothorax and metathorax metallic blue, with 

 greenish reflections, thickly covered with long yellow pile, which is 

 longer toward the ventral and posterior surfaces. Mid-dorsal carina 



foster-opleuj-d) Antet-op/eufdl 



nnterostema! Postefosterndl 



Somatochlora sEMiciECxniARis.— Abdomen of female showing markings and 



TERMS USED IN DESCRIBING THEM. 



black. Ventral and antero-dorsal edges of mesepisternum and the 

 antealar sinus yellowish. Mesepimeron with vertical, lenticular yel- 

 low spot. Metepimeron with much smaller elliptic yellow spot. 

 Wings hyaline, except brown stigma, yellow anal triangle in hind 

 wings, and white membranules, which are dusk}^ on distal two-thirds 

 in hind wing. 



General color of abdomen black, with bluish reflections on seg- 

 ments 1-3. 



The markings on the abdomen fall into two distinct series, viz, a 

 pleural or lateral scries, and a sternal or ventral series. The relation- 

 ship of these series is well shown on figure 47; also it is shown, but 

 not so well, in figures 46, 48, and 52. It appears, from a study of 

 the drawings, that in the highest development in these series there 

 would be on each segment both an anterior and a posterior spot in 

 each series. This occurs in the sternal or ventral series in both 

 sexes. (It must be remembered that in the ventral series these 

 two spots on each segment are confluent and so form a solid stripe 



'The yellow or orange on either side of the frons In Somatochlora semicircularis Is variable In extent, 

 generally not tending to meet from either side to form a transverse band separating the dark-colored 

 Irons from the dark-colored nasus. In one female specimen, however, this band Is completely present, 

 and in five males and two females it is nearly complete, being interrupted a short distance only at the 

 middle. Dr. Pliilip P. Calvert states that in some male specimens of this species from Maine the band 

 Is complete in every case. In the material upon which the present paper is based the tendency is In 

 the opposite direction; i. e., toward the obliteration of the band. 



