1. Mosquitoes, ticks, bedbugs, flies, fleas, lice, chiggers, mites … many critters blamed for bug bites are not technically bugs. “True bugs” are limited to the order Hemiptera — nitpicky types would limit them to the suborder Heteroptera — which, of the above, includes only bedbugs.
2. Some biting non-bugs do more than just bite. Female botflies, for example, attach their eggs to the underside of mosquitoes. When the mosquito lands on its victim, the eggs hatch and larvae burrow into the victim’s skin, causing painful bumps that can lead to sepsis if untreated.
3. Fleas sometimes transmit disease with their host’s help: Their bites are itchy, so the host scratches, breaking the skin and pushing in flea feces and vomit, which can be loaded with pathogens.