Looks like I still can't tell those genera apart. What characters do you look for to distinguish between the two?

Easiest way - Plagiostira has a very distinctively shaped pronotum. The the color pattern differs in construction somewhat too, notably on the pronotum. The venation of the tegmina is different in each species, but more closely reticulate in all of the Plagiostira than in this species. Genitalia differ significantly too (particularly in males), but the details may be hard to see in a photograph. It's actually easier to distinguish them in the field than in photos, because Plagiostira are so distinctive in person.

Also, this and E. kelsoensis are apparently the only species of Eremopedes that have such striking green and white coloring (though E. scudderi apparently may come close), so you don't have to look at too many options. [Though I suspect there is actually one more species involved - or - perhaps I'm wrong and this and ones like it are E. scudderi? Anyway, the ones from the Great Plains like this one look distinctly different from the ones from further to the southwest, while E. kelsoensis actually looks much less different.]

Oh, and in my experience, if you put a Plagiostira in a container with any other smaller living thing, the smaller thing will soon disappear. I haven't had that issue with Eremopedies bilineatus, and suspect they will only eat plants (????), though other Eremopedes can be agressively carnivorous.

Other species in other genera with similar patterning (as far as I can recall) all have very long thin legs.

Thanks for the characters, I'll be keeping an eye out for those now.

Maybe I should ellaborate a little on the male genitalia. The differences are species by species, but show an overlapping range of variation between these two genera. So, it's not a diagnostic difference between genera, but a striking one between some of the assorted species. The green and white banded Eremopedes are distinctly different from Plagiostira though. The upper tergite (plate) of the last segment of the male abdomen has a different shape in each species, sometimes dramatically so (rear edge with a "v"- or "u"-shaped emargination between points in E. bilineatus, cut almost all the way through the middle in several of the other species - with or without the points to either side). Also, the tooth on the inner side of the male cerci is in a different place on different species (a bit below the middle in E. bilineatus). Sometimes it's easy to see these in a photo from above.

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