332 NATHAN BANKS. 



Key to the Genera. 



1. — One pair of wings 2. 



Two pairs of wings 3. 



2. — Three setae ..Cieiiis. 



Two setae C'leou. 



3. — Hind tarsi with five joints 4. 



Hind tarsi with four joints (or less) 6. 



4. — Mesothorax scutel very large Bfetisca. 



Mesothorax scutel normal 5. 



5. — Intercalary veins in fore wing Siplilurus. 



No intercalary veins, or very few Heptageiiia. 



6. — Hind wings rudimentary, few veined, small species 7. 



Hind wings well developed, many veined 9. 



7. — Hind wings very narrow, elongate, bi-veined Ceiitroptiluni. 



Hind wings broader, obtuse, oblong 8. 



8. — Fore wings with cross-veins along whole costal area Callibcetis. 



Fore wings without Cross-veins in basal half of costal area Bietis. 



9. — Few cross-veins in basal half of costal area, three setse, most of cross-veins 



in apical half of wing, small species Epheiuerella. 



Unlike above 10. 



10. — Anal vein meets postb ran chial at base, three setae 11. 



Anal vein separated at base from postbranchial 12. 



11. — Median seta subequal to others L<eptoplilebia. 



Median seta far shorter than others Blasturus. 



12. — The % with two setae, 9 with three, J with hind legs longer than other 



pairs, white species I'olyuiitarcys. 



Unlike above 13. 



1.3. — For males 14. 



For females 16. 



14. — Median seta very rudimentary 15. 



Median seta about as long as others Ephemera. 



15. — Eyes separated by a space only as wide as ocellus, front legs not elongated, 



pale in color Pentageuia. 



Eyes separated by a space twice as wide as ocellus, fore legs elongated, 



darker in color Hexagenia. 



16. — Median seta rudimentary Hexagenia. 



Median seta subequal to others 17. 



17. — Abdominal segments 6-10 over one-half the length of abdomen. 



Ephemerae 

 Abdominal segments 6-10 not over one-half the length of abdomen. 



Peiitagenia. 



Suborder ODONATA. 



The "Dragon-flies" are among the most common of our Neurop- 

 teroid insects. Our forms have been quite thoroughly studied, but 

 the best work has, unfortunately, been published in an almost inac- 

 cessible Belgian journal. If good English descriptions were easily 



