They look a lot like mealworms, but their diet seems different. If you wanted to give a go at raising them, I'd try catching a bunch of beetles and putting them in a shoebox of soil and feeding potatoes and greens. They're known to feed on plant roots and decaying veggies, so I'd guess that potatoes may do the trick. Try it over a few weeks and see. If they lay for you, you would see the results by two months if they have the same life cycle as mealworms.
That, or just order a batch of 1000 mealworms and let some pupate and morph into beetles. It may be easier than doing some guesswork. Nutrition really does depend on what you feed the larvae, and that may be hard if you don't know what foods they'll take. Fresh fruits and veggies is a good diet for mealies, so if they'd take things like that you'd have some very nutritious feeders. Plus if you could collect your breeders locally, that would save you some money on feeders.
Now that I'm looking more at species... There are so many species of click beetles and wire worms that you're going to have to identify your local species and look up your diet. I found another forum thread on them.
click beetle colony tips?
I'm guessing this is your species:
Click Beetle (Elateridae family )
So that's why I suggested a dirt substrate.
"
Food
Adults eat pollen and nectar. Larvae eat roots."
I'm not sure how you'll achieve the adult diet, but sounds like the larvae should easily take root vegetables. Seems like you'll need to do some research. As long as you're not feeding them garbage, they should be adequate feeders. I hope you can figure out how to raise them and keep the adults alive. Seems like mealworms would be easier as a captive feeder, but this might make a fun project.
thank you!