On most of my visits to this section of the creek, I've only seen single Swift River Cruisers, flying long routes up and down the creek a few inches above the water. These individuals have proven impossible to catch, and I gave up trying to catch flying adults and concentrated instead on trying to find larvae. I've yet to find a Swift River Cruiser larva, but I did manage to find a Flag-tailed Spinylegs (Dromogomphus spoliatus) larva last July.
Wednesday, there was a little more activity on the creek, with at least four Swift River Cruisers near the pipeline cut rapids at one time, including a pair that met over the water, formed a "wheel" and flew up into the trees along creek. There were some aggressive interactions (I assume between males), and the general activity made me think that perhaps I'd catch a distracted bug looking for a mate or dealing with others of its kind. Occasionally, I would see a pair of bright green eyes zipping toward me or the yellow "taillight" as one flew past the other way. They have a maddening ability to disappear among the shallow rapids and then reappear sometimes right next to you before disappearing again.
I hadn't had any luck netting a river cruiser, and had given up for the day, when I saw an ovipositing female. I caught her while she was occupied. Once released, she returned to the riffles and continued laying eggs.
Female Swift River Cruiser (Macromia illinoiensis illinoiensis)
August 26, 2009. Four Mile Creek, Butler County, Ohio.