Centipedes in Arizona are indeed a source of concern for residents and visitors, but it is important to clarify their biological classification regarding toxicity. These creatures are not “poisonous.” Instead, centipedes are venomous organisms, meaning they actively inject toxins into a target through a specialized mechanism, typically for defense or subduing prey. All centipedes possess this ability, and the larger species found across the Arizona landscape carry a venom potent enough to cause painful reactions in humans.
The Primary Arizona Centipede
The most commonly encountered and largest venomous species in the state is the Common Desert Centipede, Scolopendra polymorpha. This centipede, often called the Tiger Centipede due to its banded appearance, can reach lengths of four to seven inches. Coloration varies widely, displaying shades of tan, brown, orange, and even blue. They are primarily nocturnal, preferring to hunt under the cover of darkness and using their flattened bodies to shelter under rocks, logs, or soil during the heat of the day.
The venom is delivered through a unique set of modified front legs called forcipules, which are located directly behind the head. These curved, pincer-like appendages contain venom glands and function like hypodermic needles to inject the toxin. A centipede will employ this mechanism only when it feels threatened, such as when it is accidentally stepped on or handled.
Understanding the Venom Effects
A sting from an Arizona centipede, particularly the larger desert species, results in an immediate and intense burning pain at the site of envenomation. This sharp sensation is often accompanied by localized symptoms like swelling, redness, and tenderness around the two distinct puncture marks left by the forcipules. These toxins are specifically designed to immobilize the centipede’s prey, which consists of insects, spiders, and occasionally small vertebrates.
While the pain level is high and may radiate up a limb, the effects are rarely medically significant for healthy adults. Symptoms typically peak within a few hours and generally subside completely within 24 to 48 hours. Systemic symptoms such as headache, nausea, dizziness, or swollen lymph glands are possible but uncommon. Any signs of a severe allergic reaction, like difficulty breathing or widespread rash, would indicate a medical emergency requiring immediate attention.
Immediate Response and Exclusion
Immediate first aid for a centipede sting involves thoroughly washing the puncture site with soap and water. Applying a cold compress or ice pack for ten-minute intervals can significantly help in reducing the pain and localized swelling. Over-the-counter pain relievers, such as acetaminophen or ibuprofen, may be used to manage the lingering discomfort. If the pain is disproportionately severe, or if the victim is a small child or infant, seeking professional medical evaluation is advisable.
Preventing entry into homes is the most effective defense. Homeowners should take several steps to exclude centipedes:
- Seal any cracks or gaps in the foundation, around doors, and window frames.
- Minimizing outdoor debris, such as woodpiles, leaf litter, and rocks near the home’s perimeter, eliminates their preferred daytime hiding spots.
- Managing moisture sources, like fixing leaky faucets and ensuring proper drainage away from the foundation.