Males won't/don't need to eat that much. Especially if they are fully grown, growing animals eat more than adults. Crickets are a good meal as long as you dust them occasionally with calcium/vitamin powder and gutload them with different fruits/vegetables/grains. Commercially available gutloads are generally pretty nutritious (at least the one's that I have tried are). If you do that crickets are a fine food source. I've noticed that milli either eat right away when you put the crickets/feeders in with them, or they will eat at their own pace as long as their is a feeder in with them. They won't stress like other Nephrurus when feeders are around them so they can be left in for longer than with knob tails. Hope that helps. I wouldn't worry as long as the tail is thick and the animal is looking good and healthy.