80 Bulletin Wisconsin Natural History Society. [Vol. 6, Nos. 1 — 2. 
SUB-FAMILY PETALUEINAE. 
A single genus, Tachopteryx, is included in this sub-family. 
But few species are known, four in all, one of which is found in 
the Union. Its range is eastern and southern. The imagoes 
resemble the Gomphidse, though they are readily distinguished 
from all other genera by the bifid median lobe of the labium. Also, 
the females of Tachopteryx have an ovipositor. 
SUB-FAMILY GOMPIIINAE. 
The species of this group include many of our large bulky 
dragon-flies. They are strong fliers, but somewhat eccentric, 
though their wings are well able to bear them. The markings of 
the body consist of olive, yellow, and black stripes. They free- 
quent flow^ing or clear water. The nymphs are predatory in habit : 
they burrow in the sand or mud in ambush, aided by their protec- 
tive coloration, or hide among the reeds, till their prey appears. 
They attack by a sudden extension of the labium, seizing their 
victim with the claw^-like lateral labial hooks. The following key 
comprises the genera found in temperate zone. Herpetogomphus 
has been eliminated, since its proper life zone is tropical. It has 
been found regionally in some parts of Arkansas and Texas, but 
never east of the Mississippi. 
1. No basal cross-vein ; legs long-, hind femora passing base of seg- 
ment 2 2 
Basal sub-costal cross-vein present ; legs short, hind femora 
hardly reaching base of segment 1 Progomphus 
2. Hind wing with anal loop 3 
Hind wing without anal loop 4 
3. Triangles free ; anal loop of three cells ; stigma broad with 
convex sides Ophiogotnphus 
Triangles crossed; anal looj) of four cells; stigma narrow^ with 
parallel sides = Hagenius 
4. Triangle of fore wing less than one fourth shorter than of 
hind wing 5 
Triangle of fore wing one third shorter than of hind wing.Lanthus 
5. Hind femora reaching to middle of segment 2, armed with 
numerous short spines Gomphus 
Hind femora reaching to base of 3 ; armed with numerous short 
and a row of strong prominent spines Dromogomphus 
PROGOMPHUS Selys, Ac. Bull. Belg. 21 (2), p. 69, 1854. 
A single species of this genus is fuond in temperate America, P. 
ohscnrns. The life Zone of this species appears to be the Upper 
Austral, and it can be expected in the Southern portions of Wisconsin. 
HAGENIUS Selys, Bull. Ac. Belg. 21 (2), p. 1854. 
A genus of two species, one from Tonkin, the other from the U. S. 
H. hrevistylus is the type. 
