A little bird told me they're Pycnoscelus femapterus. For amphibians, I would use freshly molted roaches.
A
quick search turned up this: Femapterus on the other hand have both males and females, only the males have wings and are quite a bit smaller. Fair warning nymphs are small really small. Also larger surinamensis nymphs can climb smooth surfaces and adult Male femapterus can flutter and climb, but both species spend more of their time buried. Thay like to burrow so proved them a good 2 inches of dry substrate I use a mix of leaf litter, cocofiber, sand and coconut chunk. Other than that these guys are easy to breed and keep and should make a good feeder.