What are bug bites on a cats head and ears from?

Bug bites, or possibly just follicular dermatitis, on a cat's head and ears could be due to a variety of things. I would start with external parasites including lice and mange, fleas, ticks or ear mites. If no evidence of parasites was found, I would then suspect a bacterial skin infection, which can cause raised red bumps on a cat's skin.

The good news is, most of this can be fairly easily treated by a veterinarian. You should make an appointment with your veterinarian to figure out exactly what is causing the bug bites and to get treatment started.