Hey Jay, Indeed you and Linda are right. I, too, went to the USDA site and have narrowed it down to: Ruellia nudiflora, R. caerulea, R. caroliniensis, and finally R. humilis because as you said it appears the R. prostrata is in HI. But who knows, it might have gotten here as did the imported red fire ants.
I read that one of the Ruellias was the larval plant food for the Common Buckeye butterfly and since I try to plant things for the butterflies and their larva, I went to BAMONA (Butterflies and Moths of North America) and now I can't remember which of the Ruellias it is, if it's the one which is growing out here, then we should have an ample amount of Buckeyes.
Linda, thank you for taking the time to look the plant up and putting me on the track. I do appreciate it.
Jay, thanks to you, too, for taking the time to help.
I'm much obliged to the both of you.
Lee