Black crickets are a type of field cricket that the Chinese use (a different subspecies (?) but still the same general type) for cricket fighting. They are severely aggressive and are prized for size/weight/aggression etc. Most cricket fights don't end up as actually physically dangerous, but that's because the people remove them before they can be. The species of black field cricket they use are super territorial (males) and the males will fight each other to the death if the loser cannot escape safely.
Usually with black field crickets they consume huge amounts of high energy foods, do better with higher protein levels in their diet (though it doesn't have to be from animal protein), and are territorial. All this adds up to not being good as a feeder. They are high cost animals to use as a feeder. I have kept them for fun, but they have huge mandibles (for the way they dispute territories) and getting bit by them is not fun