19081 
M uttloirshi, Dniiioii Fllcx of Wixconsiu . 
105 
SUB-FAMILY LlBELU'LIiNAE. 
This sub-family includes by far the larg-est number of dragon- 
flies of any sub-family. The species, wherever found, are abund- 
ant, and are easily recognizable by the proportionately large wings 
and their short, stout, often flat bodies. They are familiar ob- 
jects along the road-sides, often flying far from their aquatic 
homes. The thirteen North American genera separate as follows : 
1. Hind wing's narrow at the base ; triangle of fore wing level 
with the apex of the triangle of the hind wing- 2 
Hind wing-s very wide at the base; triangle of fore wing far 
beyond the level of the apex of hind triang'le 12 
2. Triang-le of fore wing* normal (three sides) 3 
Triang-le of fore wing- with four sides Nannothemis 
3. Snbtria-ng-le of fore wing- crossed; sides of triang-le niceting 
at right ang-les (90°) ; hamules of male bifid .4 
Snbtriangle of fore wing- free; sides of triangle meeting- at an 
obtnse angle (300°) ; hanmles of male not bifid .... Perithemis 
4. Hind lobe of prothorax larg-e, bilobed 5 
Hind lobe of prothorax small, entire 9 
5. Sectors of the arcnhis ped ici^llute 6 
Sectors of the arcuhis contiguous or se])arate at their orignn ; 
wing-s generally with yellow or brown marking-s. . . .Celithemis 
6. Hind wing-s with the np]:)er sector of the triangle de])arting 
from the hind angle 7 
Hind wing with the npper sector of the triangle departing 
above the hind angle on the outer side 8 
7. Leng-th of stigma more than three times the width ; face yel- 
lowish Sympetrum 
Length of stig-ma hardly twice the witlth ; face pure white. . . . 
Leucorhinia 
8. One cross-vein under the stigma, a large vacant space before 
it; hind tibite with two rows of about 10 small spines 
Pachydiplax 
Two cross-veins below the stig-ma, spaces before it nornuil : 
hind tibi?e with a row of 5 — 7 stout spines Mesothemis 
9. Sectors of the arculus contiguous at their origin ; hind wing 
with upper sector of the triangle arising from the hind angle 10 
Sectors of the arculus stalked ; hind wing- with the upper sec- 
tor of the triangle arising- above the hind angle. . . . MicrathjTia 
10. Triang-le of fore wing with two parallel cross-veins ; sub- 
triangle of 4 — 11 cehs 11 
Triangle of forewing- with a single-cross-vein ; sub-triangle 
of three cells Ladona 
11. IMale without ventral hooks on segment 1 of abdomen; female 
tibif^ longer than hind femora; sexes with similar wing- 
markings* Libellula 
IVfale with ventral hooks on seg-ment 1 of abdomen ; female 
* The male of L. piilcheUa has ventral hooks on segment 1. but this 
species is placed with LibeUula because of the other distinctions cited 
for the genus. 
