1. Lateral spines of abdominal segment 9 reaching ends of anal appendages or beyond; five palpal setae, 5 promiinent premental setae, 1-2 less prominent premental setae; abdominal segment 10 without middorsal hook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Didimops transversa
Lateral spines of abdominal segment 9 shorter, not reaching ends of anal appendages; six palpal setae, 5-6 prominent premental setae, 3-4 less prominent premental setae; abdominal segment 10 with small middorsal hook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Macromia
Key to Macromiidae Nymph Genera