I've been trying to get an answer for that too ever since he insisted that I do not have pins but I get no answer. I have not found one single other bug that crawls out of and around the butt and that causes itching. Tapeworm segments can come out alive and I may well have tapes but that is not what is causing the acute problem.
It's not actually a bite. Somewhere in all the research I've done, it said that the females crawl out and attach themselves to the skin to lay their eggs. This leaves tiny pin prick marks and feels much like a sharp pin prick but rather than painful it is extreem itching. It feels so sharp at times that it actually makes me jump. The anti-histamines are helping at least.