Species: House centipede (Scutigera coleoptrata); Millipedes, the common lookalike

What to look for

  1. Legs, counted in pairs. Adults carry 15 pairs, one pair per body segment, and on adult females the last pair is nearly twice the length of the body.
  2. Length. Penn State gives the body as one to one and a half inches (25 to 38 mm) and the overall appearance including legs and antennae as three to four inches (76 to 102 mm). Maryland gives the house centipede as about an inch long and gray.
  3. Color pattern. The legs are banded light and dark, and the body is a dirty yellow carrying three long dark stripes.
  4. Young ones look wrong. Penn State says newly hatched larvae have four pairs of legs and gain pairs at each molt, running 5, 7, 9, 11 and 13 pairs before reaching the adult 15.
  5. Centipede or millipede. Centipedes are flattened with one pair of legs per segment and never coil when disturbed, while millipedes are cylindrical to slightly flattened with two or four pairs of tiny legs per segment and most curl up when prodded.
  6. Not a centipede at all. UC IPM notes garden symphylans get mistaken for true centipedes but are white, less than 1/4 inch (6 mm) long and have 12 pairs of legs as adults.

Where and when

Penn State says house centipedes do not survive Pennsylvania winters outdoors but reproduce readily in heated structures, hiding in dark damp places by day and foraging at night. It lists harborage beneath concrete slabs, inside cement block walls, in floor drains without water traps, under stored cardboard and in crawl spaces. Maryland finds them in bathrooms, damp basements and closets, indoors and out.

Does it matter?

Penn State says house centipedes feed on silverfish, firebrats, carpet beetle larvae, cockroaches, spiders and other small arthropods, and that seeing them often signals an underlying prey problem rather than a centipede problem. UC IPM calls house centipedes beneficial and says they never damage plants or household items, while noting that some large centipedes can inflict a painful bite when provoked.

Related guides

  • Camel cricket: A camel cricket is the humpbacked, wingless, long-legged cricket that jumps out of a basement corner.
  • Silverfish: A silverfish is a wingless, flat, teardrop-shaped insect covered in silvery scales, with long thread-like antennae and three tail-like appendages at the rear.
  • Earwig: An earwig is the flat, dark reddish brown insect with a pair of claw-like pincers at the rear.

Sources