The tropical tentweb orbweaver, scientific name Cyrtophora citricola, has spread throughout the Miami-Dade county area since April 2000. It builds large, tight webs, typically on fences. Orbweavers can change color to blend in with their surroundings. Females are larger than males. Their extensive webs -- although not the spiders themselves -- can kill small, young trees and foliage.
The common house spider, or Achaearanea tepidariorum, thrives throughout Florida, including Miami. It can cause a scare because it resembles a widow spider, but it's not dangerous. The southern house spider, Kukulcania hibernalis, is large and looks much like a brown recluse. Its bite can be painful and cause swelling, but its venom is not dangerous.
Recluse or Violin Spiders
Recluse spiders are not indigenous to Florida, but three species have relocated to the peninsula area, and the Mediterranean recluse or Loxosceles rufescens, has appeared in Miami. Recluses are quiet and shy, but have a nasty venomous bite for which there is no effective antivenin. They tend to hide during the day, often in closets and clothing. Also called violin spiders due to dark violin-shaped spots on their back, recluses cause scabbing and dead tissue when they bite.
Two widow species appear in Florida in the southern peninsula area, including Miami: the Lactrodectus mactans, or red widow spider, and the Latrodectus geometricus, the brown widow. The red widow has reddish, or sometimes orange, spots on its abdomen, and a brown pattern with an orange hourglass shape appears on the abdomen of the brown recluse. Both species create webs close to the ground, but can also build them higher. Red widows like small palm leaves; brown widows prefer man-made structures, such as houses, outdoor furniture and fences. Though dangerous, you'd have to provoke one into biting you. Bite symptoms can include intense muscle pain and rigidity, shortness of breath and headaches.
If you live in the Miami area and a spider bites you, try to capture it. Save it in a jar filled with rubbing alcohol or mouthwash, and take it to the doctor or emergency room with you. Because house spiders can closely resemble widows and recluses, it’s best to have the spider with you for accurate identification. Antivenin exists for widow bites, and calcium gluconate can reduce the pain. The symptoms will also usually go away in a few days on their own. Don’t try to cut away the affected skin if you suffer a recluse bite. Medications exist to stop the spread of tissue damage, taken as soon as possible after the bite.