Centipedes are multi-legged arthropods widespread throughout California, often prompting concern when they move from outdoor habitats into human dwellings. These creatures are predators that use venom to subdue their prey, which is the root of most public anxiety regarding their presence. While their appearance can be alarming, the danger they pose to humans depends heavily on the specific species involved and its size. Understanding the differences between common types, their defensive mechanisms, and simple prevention steps can help residents coexist safely with these local inhabitants.
Identifying Centipedes in California
Centipedes in California fall into two groups that differ greatly in size and medical significance. The most frequently encountered species inside homes is the House Centipede (Scutigera coleoptrata). This species is recognizable by its yellowish-gray body, three dark longitudinal stripes, and 15 pairs of long, banded legs. While its body is only 1 to 1.5 inches long, the trailing legs make it appear much larger, and its delicate structure allows it to move with surprising speed across surfaces.
The House Centipede is not considered a serious threat to human health, as its small mouthparts rarely pierce human skin. Conversely, the Common Desert Centipede (Scolopendra polymorpha), also known as the Tiger Centipede, presents a more significant concern, particularly in the drier, southern regions of the state. This species is far more robust, commonly reaching lengths of 4 to 7 inches, and displays highly variable coloration, sometimes appearing with a red or orange head or a distinctive blue color.
S. polymorpha primarily lives outdoors under rocks, logs, and debris in grasslands and desert environments. All centipedes are characterized by having only one pair of legs per body segment, which distinguishes them from millipedes, which have two pairs per segment. The venom apparatus consists of forcipules, which are modified front legs that curve around the head and function as claws to inject toxins.
Severity and Treatment of Centipede Bites
A centipede “bite” is an envenomation delivered by the specialized pincer-like forcipules, which puncture the skin and inject venom, often leaving two distinct marks in a chevron pattern. The severity of the reaction depends on the centipede’s size. Envenomations from large species like Scolopendra polymorpha cause immediate, intense, localized pain, accompanied by swelling and redness at the wound site. These symptoms can persist for several hours to a few days.
While painful, centipede envenomations in California are rarely life-threatening to healthy adults. Systemic effects such as dizziness, headache, or nausea are possible but uncommon, and the greatest risk is associated with young children or individuals who develop an allergic reaction.
The initial first aid involves washing the wound thoroughly with soap and water to prevent secondary infection. Applying a cold compress for 10-minute intervals can help reduce pain and swelling, as can the application of heat due to the heat-labile nature of the venom. Contact a poison control center for guidance, even if symptoms appear minor. Seek professional medical attention immediately if signs of a severe allergic reaction occur, such as difficulty breathing, hives, or swelling of the throat or face. Medical treatment focuses on managing symptoms and may include antibiotics if a secondary bacterial infection develops.
Structural and Environmental Prevention
Minimizing the presence of centipedes around and inside a home requires a two-pronged approach focused on structural exclusion and environmental control. Centipedes are attracted to dark, damp environments and the presence of small pests that serve as their food source.
The first step involves sealing all potential entry points into the structure, including cracks and gaps in the foundation, around utility pipes, and under doors. Installing tight-fitting door sweeps and ensuring window and door screens are intact eliminates common routes for centipedes to enter the living space.
Controlling the immediate outdoor environment is also necessary, as centipedes seek shelter in debris close to the home. Clearing away leaf litter, woodpiles, mulch, and stones resting directly against the foundation removes their preferred hiding and breeding habitats.
Inside the home, reducing moisture is a highly effective deterrent, since centipedes are prone to desiccation and thrive in high-humidity areas. This can be achieved by using dehumidifiers in basements and crawl spaces, improving ventilation in bathrooms, and promptly fixing leaking pipes or faucets. Controlling populations of other household pests, such as silverfish and spiders, also removes the centipede’s primary food source, making the environment less appealing.