GOMPHUS 85 
Four fairly well defined subgenera are recognizable in our fauna, and, 
to further facilitate identification, these groups will be characterized, 
and supplemental keys supplied, for the species of each group. The 
known nymphs will be tabulated also under the four subgenera to which 
they seem to belong. 

Nymphs 
Labium Abdomen 
Name m. lobe! | lat. lobe? | teeth? | width‘ |lat.sp.5| groove® 9:87 
Gomphurus | convex variable | 4-11 | wider | 6-9 long equal 
Gomphus convex pointed | 4-10 | wider | 6 or 7 | variable | equal 
to 9 
Stylurus straight hooked | 3-4 not | 6-9 long greater 
wider 
very con- 
Arigomphus | vex, with | pointed | 6-7 | wider! 7 or 8 | wanting | greater 
med. tooth to 9 
1 Front border of median lobe. 
2 End of lateral lobe. 
3 Teeth on inner margin of lateral lobe. 
4 Width of abdomen as compared with width of head. 
5 Lateral spines on abdominal segments. 
6 Middorsal groove or impressed line on abdomen. 
7 Length of ninth as compared with eighth abdominal segment. 
Subgenus GompHurus Needham 
Here belong some large species with a very broadly expanded and 
and club-shaped abdomen, and some smaller stocky species that are 
little expanded; but all are characterized by thick heavy bodies, and 
(except in the first five species) squarely cut terminal abdominal seg- 
ments. The hamules of the male stand perpendicular to the axis of 
the abdomen or nearly so, and the subgenital plate of the female is 
rather large. 
The nymphs of the group are broader and flatter of abdomen and 
more blunt at the apex than any others of the genus Gomphus. The 
lateral spines are rather long, especially those of the ninth segment. 
The tenth segment is short, annular and included. The following tabu- 
lar statement of the characters of the nymphs of those species that 
have hitherto (1928) been reared will help in their recognition. 
