A lot of people use nothing for the body, just bare thread. I like the peacock just because it looks good to me, try different things. I think you need something with a little bulk to show underneath.

The body of a foam beetle consist of peacock herl. If you look at a strand of herl, you find one side is dark and the other is metallic green. The green color is what we want showing for the thorax. Also, most peacock herls have a skimpy area at the base of the herl. Cut that part off.
Hold two herls in your left thumb and forefinger with the green sides together and against the thumb. Place herls at a downward angle where you tied in wing case. Make loose wrap of thread and tighten.
Continue heavy wraps forward securing peacock herl butts.
Leave thread hanging at around 4/5 to 5/6 of hook shank near hook eye.
Wrap herl forward with each wrap along side previous wrap and completely covering thread. I wrap herl using my right hand but switch to left and then back to right to avoid hanging thread and bobbin.
Watch hook point.
Wrap till you cover thorax area but leave room at hook eye for leg material tie in and wingcase tie off. Most beginners crowd the eye with too much material and have trouble whip finishing.
Tie off peacock herl with tree or four wraps of thread.
Cut excess herl and secure with 5 or 6 more wraps of thread.
Take thread and palmer thread around thorax to wingcase and back to hook eye. It should only take 4 or 5 wraps total. This reinforces the delicate herl.