Scorpions and Centipedes

Scorpions and centipedes are two groups of arthropods that nobody wants in their homes. Both of these animals have the capability of stinging (scorpions) you or biting (centipedes) you with painful results. Only one species of scorpion in this country is dangerously venomous. It is the bark scorpion (Centruroides sculpturatus) found mostly in Arizona but also southwestern New Mexico. It has killed a few people in Arizona, but not in the last 40 years. Centipede bites are painful, but not deadly in this country. There are some very large centipedes in Asia that have caused human fatalities, but none in the United States. However, anyone can be allergic to anything, including the bite or sting of an insect or some other arthropod. Even if they bites or stings aren’t fatal, they can certainly be painful.

There are over two hundred species of centipedes in the western U. S., but most of them are very small and belong to two suborders. They are the stone centipedes (Lithobiomorpha) and the soil centipedes (Geophilomorpha). Stone centipedes are about an inch long and have 15 pair of legs. Soil centipedes aren’t much longer and have upwards of 40 pair of legs. Neither group is capable of biting people. Both are common in yards and feed on small bugs including some pests, so they can be considered beneficial. House centipedes (Scutigera coleoptrata) are about an inch long and have 15 pair of very long legs. They are common almost everywhere and are often found in homes. They rarely bite and they do feed on such pests as spiders, bed bugs, termites, cockroaches, ants and silverfish, so they should probably be welcome in the home.

Three species of Scolopendromorpha centipedes are found in the western states. The desert centipede (Scolopendra polymorpha) is most common throughout throughout the west with the exception of Washington. It is about three or four inches long. The green centipede (Scolopendra viridis) is found in the mountainous areas of New Mexico, Arizona, southeastern Colorado, Utah and extreme southern Nevada. It is only a couple of inches long. The giant desert centipede (Scolopendra heros) is found in the southern and eastern portions of New Mexico, much of Arizona and the extreme southeast portion of Colorado. This species can reach a length of 6.5 inches and is capable of killing and eating mice. All of the Scolopendra have painful bites but they are not dangerous.

Centipedes and scorpions are usually found in areas of high moisture such as loose bark, in rotting logs, under stones, boards, railroad ties, trash, piles of leaves and grass clippings and similar areas. They are nocturnal or active at night and hide by day in the earth, wandering forth by night to hunt. They occasionally invade structures and will feed on cockroaches, cricket, spiders, etc. Although they may be found anywhere in a building, including beds, the usual places are damp basements, bathrooms, and any crawl space under the home or building. Exclusion to keep them out of structures is most important, and this begins with ensuring that no tree or shrub branches are touching the structure. The branches can be pruned away to eliminate this common pathway. You also can carefully examine the entire exterior, including up to the eaves as scorpions and other pests may crawl up rough surfaces, and you want to permanently fill in any openings found and ensure all vent screens are in place and in good condition. In the yard you can eliminate many potential harborage sites for scorpions and centipedes such as rocks, boards, and other objects resting on the soil. Scorpions will also hide under bark on trees, so these can be can be dusted with food grade diatomaceous earth where loose bark is found.

Firewood should be stacked on racks off the soil and kept outside until immediately ready to burn. Garbage cans should be on racks to elevate them. Grass should be mowed to prevent hiding areas for scorpions. centipedes and other pests and weeds should be eliminated.

If you find a scorpion or centipede in your home, spray it with some Greenbug for Indoors. Don’t use synthetic pesticides as they are more dangerous than the scorpion or centipede.