If you feel a sting and don't know what caused it, you're probably the victim of a no-see-um. You can expect more where that came from. No-see-ums, also known as sandflies, are actually biting midges that can be extremely bothersome along the saltwater coast, especially at sunrise and sunset.
Five species are believed to inhabit coastal areas (Culicoides furens, C. mississippiensis, C. hollensis, C. harbosai, and C. melleus). Appropriately named, they appear as little more than a tiny black speck on your skin, but there's no mistaking their sharp bite.
No-see-ums can't bite through clothing. Most strong insect repellents will also keep them away. Skin-So-Soft, a bath oil made by Avon, is also known to defeat no-see-ums, but has little effect on saltwater mosquitos. Campers should be aware that only the smallest screening will keep them out of your tent or RV.