No. 39] ODONATA OF CONNECTICUT: AESHNIDAE 171 



2. Palpi with large teeth on mesal margins (PI. vi, Fig. 2) ; a dorsal 



ridge present on abdominal segments 7, 8, and 9; antennae 6- 



segmented Epiaeschna, p. 195 



Palpi without large teeth on the mesal margins ; no dorsal ridge 

 on segments 7, 8 and 9 ; antennae 7-segmented 3 



3. Caudo-lateral margins of the head distinctly angulate or, if obtusely 



angulate or rounded, then the lateral terminal appendages only 



one-fourth the length of the inferiors 4 



Caudo-lateral margins of the head rounded, or if obtusely angulate, 

 then the lateral anal appendages more than one-fourth the length 

 of the inferiors 5 



4. Proximal segment of the labial palpi squarely truncate at the 



apices ; lateral anal appendages about one-fourth the length of 

 the inferiors ; distal margin of the mentum with a small pointed 

 tooth on each side of the median cleft (PI. vi. Fig. 8 ; Fig. 7, 



Nos. 6, 7) Boyeria, p. 172 



Proximal segment of the labial palpi not squarely truncate at the 

 apices ; lateral anal appendages more than one-fourth the length 

 of the inferiors ; distal margin of the mentum without a pointed 

 tooth on each side of the median cleft (tooth rounded if present) 



Basiaeschna, p. 174 



5. Surface of cuticle of abdomen smooth, shining; lateral marginal 



spines on abdominal segments 7 to 9 ; basal segment of male 



superior appendage truncate at apex Anax, p. 177 



Surface of the cuticle not smooth, usually dull ; lateral marginal 

 spines on abdominal terga 5 or 7 to 9, usually 6 to 9; basal seg- 

 ment of the superior appendage bluntly pointed at tip Aeshna, p. 179 



Adults 



1. Thorax uniform green; M2 (PI. ix. Fig. 2) making a bend towards 



Ml at the distal end of the stigma ; anal angle of wings similar in 

 tlie two sexes : abdomen with 2 lateral ridges on each side of 



terga 4-8 Anax, p. 177 



Thorax with more or less brown or black ; M2 not bending towards 

 Ml at the distal end of the stigma; anal angle of the wings dis- 

 similar in the two sexes ; abdomen with a single lateral ridge 

 on each side of terga 4-8 2 



2. Basilar space with more than one cross-vein (PI. viii, Fig. i) .. 



Boyeria, p. 173 



Basilar space without or with a single cross-vein 3 



3. Rs forked 4 



Rs not forked 6 



4. Length of abdomen over 55 mm. ; hind wings 55 mm. (Fig. 39) . . 



Epiaeschna, p. 195 

 Length of abdomen usually less than 55 mm. ; hind wings not over 

 50 mm. in length 5 



5. Cephalic section of arculus longer than the caudal ; only one row 



of cells between Rs and the R supplement (PI. viii. Fig. 3) 



Nasiaeschna, p. 193 

 Cephalic section of the arculus shorter than the caudal section ; 

 more than one row of cells between Rs and the R supplement 

 (PI. IX, Fig. i) Aeshna, p. 179 



6. Supertriangular area free from cross-veins (PI. xir. Fig. 3) ... 



Gomphaeschna, p. 176 



Supertriangular area with cross-veins (PI. viii, Fig. 4) 



Basiaeschna, p, 174 



