334 NATHAN BANKS. 



Subgenera of AGRION. 



1. — No spine at end of eighth segment of 9 2. 



A spine at end of eighth segment of 9 6. 



2. — Lower sector of triangle arising before tne basal postcostal nervuri' 3. 



Lower sector of triangle arising at or after the, basal postcostal nervure. 



Erythragrion. 

 3 — Two postooular spots 4. 



No postocular spots 5. 



4. — Abdomen very slender, color metallic-green Nehalennia. 



Abdomen less slender, color less metallic Agrion. 



5. — Color red Pyrrhosoma. 



Color bronzed on blue or yellow Erythromma. 



6 — Tenth segment of % a little prolonged above .. 7. 



Tenth segment of % not prolonged above Enallagma. 



7. — Inferior sector of triangle arising before the basal postcostal nervure 8. 



Inferior sector of triangle arising at basal postcostal nervure. ..Oxyagrion. 

 8. — Two postocular spots 9 



No postocular spots Amphiagrion. 



9. — Pterostigma of "J, removed from costa Anomalagrion. 



Pterostigma of % uoiraal Ischnura. 



GOMPHID^. 

 1. — Labium entire 2 



Labium bifid, pterostigma very long Tachy<»ptei*yx. 



2. --Triangle with transverse veins 3. 



Triangle without transverse veins Oonipl. "^<. 



3. — Superior side of triangle longer than interior 4 



Superior side of triangle shorter than interior <jioiii|)lioide)>' 



4— Feet short Pro^ompli' /«. 



Feet very long Hageiiitis. 



Subgenera of GOMPHUS. 



I. — Wings Savescent at base Herpetogomphus. 



Wings not flavescent at base 2. 



2. — Thorax almost wholly greenish, dark marks faint, narrow and brownish. 



femora mostly yellow Ophiog-omphus 



Thorax with dark marks more distinct, broader, often coiitltient, legs mostly 



black 3 



3. — Hind femora extremely long and s])inoiis Dromog'oraphus 



Hind femora not very long or spinous 4. 



4.— Dorsum of thorax with a single, median, yellow spot Octogomphus. 



Di>rsum with lateral yellow or green stripes Gomphus 



CORDULEGASTERID^. 



We have but one genus { Cor duleg aster) in this family. 



^SCHNID^. 

 L— Triangle with one transversal Goini>liie!i>cliiia' 



Triangle with two or more transversals , 2. 



