Pest group
Spiders & Crawlers
Spiders, scorpions, ticks and the many-legged crawlers found in basements and yards.
Identify at a glance
Size, key marks and where each spiders & crawlers pest shows up first, with the threat level and the first step to take.
| Pest | Threat | Size and key marks | Where to look | First step |
|---|---|---|---|---|
| Spiders | Moderate | 1/16 to 3 inches including legs (2–75 mm). Eight legs, two body parts; brown recluse has a violin mark, black widow a red hourglass. | Basements, garages, corners, window frames, woodpiles | Vacuum webs and egg sacs |
| Scorpions | High | 1 to 3 inches (25–75 mm). Pincers, segmented tail with stinger; glow under UV light. | Southwest homes: walls, attics, closets, shoes, landscape rock | Weatherstrip doors and seal weep holes with mesh |
| Ticks | High | 1/32 to 1/4 inch (1–6 mm) unfed. Flat, oval, eight legs (adults); swell greatly after feeding. | Tall grass, leaf litter, wooded edges; on pets and people | Keep grass short and remove leaf litter |
| Centipedes | Low | 1 to 1.5 inches body (25–38 mm). Up to 15 pairs of long legs; very fast; yellowish with dark stripes. | Basements, bathrooms, closets, crawl spaces | Dehumidify basements and fix leaks |
| Millipedes | Low | 1 to 1.5 inches (25–38 mm). Slow, round, many short legs; curl into a coil. | Mulch, leaf litter, basements and garages after rain | Pull mulch back 12 inches from the foundation |
When to call a professional
- SpidersBrown recluse spiders found indoors repeatedly
- ScorpionsBark scorpions seen indoors more than once
- TicksA rash, fever or aches in the weeks after a tick bite (see a doctor)
- CentipedesLarge numbers that point to a hidden moisture or insect problem
- MillipedesMass migrations every year despite habitat changes
Latest spiders & crawlers guides
Other pest groups
- Household InsectsAnts, roaches, bed bugs and the other insects that move indoors for food, water and warmth.
- Bees & WaspsNests under eaves, in walls and in the ground: when to leave them, when to act and how to stay safe.
- Rodents & ShrewsMice, rats, squirrels and their relatives: signs, traps, exclusion and cleanup.
- Lawn & Garden PestsDiggers and grazers that tunnel lawns, raid vegetable beds and undermine foundations.
- WildlifeRaccoons, skunks, bats, snakes and birds: humane removal, repellents and the laws that apply.
Photo credits
Thank you to Ryan Hodnett, Shenrich91 and Courtesy of NIAID Ryan Kissinger for sharing these beautiful photographs and helping bring this guide to life.