I was looking through my dragonfly photos this morning when it suddenly dawned on me that this nymph -- which I found in the Doyles on 9/2 of last year -- was not the clubtail dragonfly that I normally see. The nymphs that I normally see have wingpads that are parallel to the body: they look like this.
Perplexed, I decided to key out both types and here's what I found.
17a Naked antennal segment 4 generally about 1/2 as long as hairy segment 3..........Progomphus
17b Segment 4 of antennae vestigal or nearly so.......18
We've got the latter as I'll show in a moment. So on to 18.
18a Wingpads strongly divergent........... Ophiogomphus
18b Wingpads laid parallel along back........19
Here you go.
Ophiogomphus for sure. Hmm... But I'm quite sure that I thought the other nymph was Ophiogomphus. Time to explore. On to 19.
19a Body very flat: abdomen nearly circular in dorsal view; paired tubercles on top of head....... Hagenius
19b Abdomen more nearly cylindrical; no tubercles on head....... 20
19a describes genus Hagenius, and I've found quite a few of those over the years.
We move on to 20.
20a Antennal segment 3 flattened and oval, nearly as wide as long.... 21
20b Long antennal segment 3 more or less cylindrical....... 22
Definitely "nearly as wide as long." On to 21.
21a Antennal segment 3 widest proximally..... Stylogomphus
21b Antennal segment 3 widest near middle, about 2 times as long as wide and rounded apically....Lanthus
Lanthus. Got it. And I find that one a lot. But for me, Ophiogomphus is a new one. Have to add that one to my list of taxa.