68 Bulletin Wisconsin ^'atural History Society. [Vol. 6. Nos. 1 — 2. 
Tropical genera, however, show really gigantic forms, measuring 
in expanse of wing from 5-^8 inches. The habits of our 
northern representatives are similar to those of the preceding sub- 
family. They seek the low sedges of river bottoms and beaches in 
search of food or unwary mates ; for, small as they are, they are 
said to be cannibalistic to a great extent. Small, but graceful 
fliers, they are varied in color, some dull green, some a beautiful 
violet, others priding a mixture of red, green and orange. 
1. Median and snbmedian sectors arising near the nodus 2 
Median and snbmedian sectors arising- near the arculus Lestes 
2. Spines of the tibite short 3 
Spines of the tibi^3e twice as long as the spaces between them . . 
Argia 
3. No postocular spots 4 
Postocular spots present 5 
4. Colors blue and black Erythromma 
Colors red and black Amphiagrion 
5. Pterostigma of front and hind wings similar 6 
PterostigTOa of front and hind wings dissimilar in color ; an 
anical bifid process on dorsum of 10 7 
6. Nodal sector arising near the fourth postcubital on fore wing\ 
near the third on hind wing; abdomen about 20 mm. .Nehallennia 
Nodal sector arising near the fifth postcubital on fore wdng\ 
near the fourth on hind wing; abdomen about 25 mm. .Enallagma 
7. Pterostigma of fore wnngs normal, darker than of hind wing. . 
Ischnura 
Pterostigma of fore wings removed from costa, lighter than 
of hind wing Anomalagrion 
The foregoing table accounts only for the generic characters of 
the males. The females, especially of the three last g*enera enumerated, 
are so vitally different from the males, even structurally^ that it is 
Avell-nigh impossible to bring them under a uniform arrangement with 
the males. For that reason I have compiled a separate one for the 
females. Lestes and Argia are omitted, since the females of these 
genera distinguish themselves sufficiently from all others, Lestes by the 
venation, and Argia by the armature of the tibiae. 
1. Bristles of the tibiae short ; no apical spine on sternum of 8. . . . 2 
Bristles of the tibiae short ; an apical spine on sternum of 8 ... . 3 
2. No postocular spots ; colors blue and black ; length of abdomen 
about 28 Erythromma 
Postocular spots present ; colors bronzy green ; slender species, 
length of abdomen about 20 Nehallennia 
3. Postocular spots present 4 
No postocular spots; colors red and black Amphigrion 
4. Nodal sector arising near the fourth postcubital on the fore 
wing, near the third on the hind wing 5 
Nodal sector arising near the fifth postcubital on the fore wing, 
near the fourth on the hind wing Enallagma 
5. Less than three basal segments of abdomen orange Ischnura 
Four basal segraents orange or yellow Anomalagrion 
LESTES Leach. Edin. Encyl., 9, p. 137, 1815 ; Needham. Broc. U. 
S. Nat. Mus., 26, p. 710, 717, 720, 1903 (Venation). 
