NORTH AMERICAN ODONATA. 221 



B. 9 with an apical ventral spine on 8. 

 No pale postocular spots. 

 Pterostigma similar on front and hind wings; color red; % with no 



bifid process on dorsum of 10 7. Aiiipliiagrioii. 



A pale (postocular) spot behind each eye. 



Pterostigma of % similar in color on front and hind wings, no dorsal 

 bifid process on 10 (except in E. exsnlans %). Nodal sector ( 'J, 9 ) 

 arising near 5th postcubital on front wings, 4th on hind wings, or 



more remote 8. EuHllagnia. 



Pterostigma of % dissimilar in color on front and hind wings, 10 with 

 a dorsal process ( % ) bifid at its apex. 

 Pterostigma of % touching the costa on front wings, darker than on 

 hind wings. Front wings ( '^ 9 ) with usually more than 7 postcu- 

 bitals. (The species included in this catalogue have the nodal sector 

 usually arising at the 4th postcubital on the front wings, at the 3rd 

 on the hind wings; this aids in distinguishing from Enallagma.) 



9. Ischnura. 

 Pterostigma of % not touching the costa on the front wings. Front 

 wings ( 'J) 9 ) with usually, but not always, less than 7 postcubitals. 

 Nodal sector arising not farther than the 4th postcubital. 



10. Anomalagrion. 



Subfamily 3. GOMPHIN^. 



I. Median labial lobe bifid. 



Legion Petalura Selys.* — Basilar space free ; triangles of front wings crossed ; 

 membranule very small ; 9 with genital valves. 

 Triangle of front wings with the upper side longer than the inner, the outer 

 longest; hair-like termination of antennae jointed; % superior appen- 

 dages not more than twice as wide in front of apex as at base, inf. app. 

 more than half as wide at base as long 11. Tachopteryx. 



II. Median labial lobe entire ; basilar space free. No genital valves. 

 Legion Oomphoides Selys. — All or some of the triangles crossed ; membranule 



wanting, or very small. 

 Feet long, hind femora reaching backwards to base of 3; discoidal triangles 

 crossed, internals and supratriangular spaces free; abdomen blackish, 



with a dorsal yellow stripe 12. Hageiiius. 



Legion Gomphus Se\js. — All the triangles and the supratriangular spaces free; 

 membranule wanting, or very small. 

 % . Inferior appendage bifid, its branches almost contiguous. 10 Considerably 

 shorter than 9. % inf. app. bifid in its apical half, blanches straight, 

 upcurved at apex. 9 • Vulvar lamina nearly as long as 9 (except in the 

 European 0. serpentinus), divided into two narrow, quite long, parallel, 

 almost contiguous branches, pointed at their apices. 



13. Ophiogoiuphus. 



* It may hereafter be necessary to regard this as representing a distinct sub- 

 family — the Petal uriuaj. 



TRANS. AM. ENT. SOC. XX. AUGUST, 1893. 



