To answer your beetleforum request: Cotinis mutabilis, which is very similar to nitida, can be found drinking from soft fruits in trees and certain kinds of sap. They do not seem to know that transparent objects are a barrier, and I've mostly collected them from a deer-netting fence used for unrelated purposes (accidental flight-intercept trap!). But beware of flight-intercept traps they can get tangled up in, like deer and tennis nets, because they may get trapped and die if not saved (see my blog at popular cockroach section). Also remember that Cotinis is a flower beetle and normally buries itself in dirt at night, so you should hang or "paint" fermenting (NOT moldy) fruit/other sugary stuff (some markets may give you fermenting fruit for free) in trees during the day if you have no fruit bushes/fruit trees around.
As for grapevine beetles, Orin's Ultimate Guide to Breeding Beetles says that they should be collected at lights and that grubs live in various rotten woods.
He also says somewhere else in the book that Dynastes tityus occurs at low densities, so gas station lights are better than blacklights because there are a lot of gas stations and all those stations combined cover a wider area than one blacklight can. I suspect you are facing the same problem with your grapers and you should check gas stations and other public lights to get a good haul of grapeviners.
Remember, the best way to catch insects is to figure out their behavior, habitat, diet, hosts, etc. and then use or invent strategies that exploit one or more of those aspects. Cheers!
