Gray Bugs: 25 Common Types to Know
Found a gray bug? This guide lists 25 common bugs that are gray in color, ordered from most to least risky, with the one feature that identifies each.
Quick list
- American Dog Tick
- Mosquito
- Blister Beetle
- Head Louse
- Horse Fly
- Wheel Bug
- Wolf Spider
- Brown Marmorated Stink Bug
- Drain Fly
- Fungus Gnat
- House Centipede
- House Fly
- Longhorn Crazy Ant
- Silverfish
- Southern House Spider
- Spotted Lanternfly
- Squash Bug
- Booklouse
- Cellar Spider
- Common House Spider
- Crane Fly
- Eyed Click Beetle
- Harvestman
- Pill Bug
- Springtail
How to narrow it down
Narrow it down with three quick checks. Count the legs: insects have six, spiders and ticks have eight, and centipedes and millipedes have many more. Check for wings, even folded ones. Then compare size against a coin: a US penny is 19 mm across. Our bug identifier tool does this filtering for you.
The 25 bugs
American Dog Tick
American Dog TickDermacentor variabilisA brown tick with ornate white-gray markings on its shield, common along trails, roadsides and grassy fields. It readily feeds on dogs and people.
Tell-tale sign: Brown body with silvery-white mottling on the shield. Risk: American dog ticks can transmit Rocky Mountain spotted fever and tularemia.
Mosquito
MosquitoCulicidae (e.g. Aedes albopictus)A small, slender fly whose females bite to take blood for egg production. The Asian tiger mosquito is black with white stripes and bites aggressively during the day.
Tell-tale sign: Long, needle-like mouthpart (proboscis). Risk: Mosquito bites itch and, depending on the region, can transmit West Nile, dengue and other viruses.
Blister Beetle
Blister BeetleEpicauta spp.A long, soft-bodied beetle with a narrow neck that feeds on flowers and vegetable foliage. Its body contains cantharidin, a chemical that raises blisters on skin.
Tell-tale sign: Long, soft, cylindrical body with flexible wing covers. Risk: Handling or crushing blister beetles can cause painful skin blisters, and hay contaminated with them can poison horses.
Head Louse
Head LousePediculus humanus capitisA tiny, wingless insect that lives only on the human scalp and feeds on blood. Its eggs, called nits, are glued firmly to hair near the scalp.
Tell-tale sign: Sesame-seed-size tan or grayish insect on hair. Risk: Head lice are itchy but don't spread disease; they spread mainly by head-to-head contact.
Horse Fly
Horse FlyTabanus spp.A large, stout fly with huge eyes that pursues people, horses and cattle for blood. Females slice skin with blade-like mouthparts, causing a sharp, painful bite.
Tell-tale sign: Large, heavy body with very large, often iridescent eyes. Risk: Horse fly bites are painful and can swell; they rarely transmit disease to people in the US.
Wheel Bug
Wheel BugArilus cristatusA large, gray assassin bug with a raised, toothed crest on its back that looks like half a gear wheel. It hunts caterpillars and beetles and is a garden ally.
Tell-tale sign: Semicircular, cog-like crest on the thorax. Risk: Its bite is extremely painful and can take days or weeks to heal, so avoid handling it.
Wolf Spider
Wolf SpiderLycosidae familyA large, hairy, fast-running spider that hunts on the ground instead of building webs. Females carry their egg sacs and then their spiderlings on their backs.
Tell-tale sign: Hairy brown or gray body with dark stripes. Risk: Wolf spiders can bite if handled, causing pain and swelling like a bee sting, but they're not dangerous.
Brown Marmorated Stink Bug
Brown Marmorated Stink BugHalyomorpha halysA shield-shaped, mottled brown bug that invades homes in fall to overwinter and feeds on fruit and vegetables in summer. It releases a sharp odor when disturbed or crushed.
Tell-tale sign: Shield-shaped, marbled brown body. Risk: Stink bugs don't bite or sting people; they are a household and crop nuisance.
Drain Fly
Drain FlyClogmia albipunctataA small, fuzzy, moth-like fly that rests on bathroom walls near sinks, tubs and floor drains. Its larvae live in the slimy film inside drains.
Tell-tale sign: Fuzzy, gray, leaf-shaped wings held roof-like over the body. Risk: Drain flies don't bite and aren't known to spread disease in homes.
Fungus Gnat
Fungus GnatBradysia spp.A tiny, dark, mosquito-like fly that hovers around houseplants and windows. Its larvae live in moist potting soil and feed on fungi and roots.
Tell-tale sign: Delicate dark body with long legs and antennae. Risk: Fungus gnats don't bite; larvae can damage seedlings and young roots.
House Centipede
House CentipedeScutigera coleoptrataA fast, yellowish-gray centipede with 15 pairs of very long legs that races across floors and walls at night. It hunts silverfish, cockroaches and spiders.
Tell-tale sign: Fifteen pairs of long, banded legs. Risk: House centipedes rarely bite; a bite feels like a mild bee sting.
House Fly
House FlyMusca domesticaThe most common fly in homes, a dull gray fly with four dark stripes on its thorax. It breeds in garbage, manure and rotting food and lands on nearly everything.
Tell-tale sign: Four dark lengthwise stripes on a gray thorax. Risk: House flies don't bite, but they can carry bacteria that cause food poisoning.
Longhorn Crazy Ant
Longhorn Crazy AntParatrechina longicornisA dark, slender ant with extremely long legs and antennae that runs in fast, jerky, seemingly random paths. It nests in soil, trash and wall voids, mostly in warm southern states.
Tell-tale sign: Long legs and antennae relative to its body. Risk: Crazy ants rarely bite and don't sting; their sheer numbers make them a nuisance.
Silverfish
SilverfishLepisma saccharinaA wingless, carrot-shaped insect covered in silvery scales that moves with a fish-like wiggle. It eats paper, glue, starches and fabrics in damp areas.
Tell-tale sign: Silvery-gray, teardrop-shaped, scaly body. Risk: Silverfish don't bite; they damage books, wallpaper and stored papers.
Southern House Spider
Southern House SpiderKukulcania hibernalisA velvety, dark gray to brown spider of the southern US whose males look like brown recluses. Females build radiating, lint-like webs around cracks in walls and windows.
Tell-tale sign: Velvety, uniformly dark females with a small head. Risk: Southern house spiders rarely bite and are not medically significant.
Spotted Lanternfly
Spotted LanternflyLycorma delicatulaAn invasive planthopper spreading through the eastern US that feeds on grapevines, maples and tree of heaven. Its folded gray forewings hide bright red hind wings.
Tell-tale sign: Gray forewings with black spots. Risk: Spotted lanternflies don't bite or sting; they damage vineyards and leave sticky honeydew.
Squash Bug
Squash BugAnasa tristisA flat, grayish-brown bug that sucks sap from squash and pumpkin vines, causing leaves to wilt and turn crispy. Clusters of bronze eggs appear on leaf undersides.
Tell-tale sign: Flattened, dull gray-brown body. Risk: Squash bugs don't harm people; they can wipe out squash and pumpkin plants.
Booklouse
BooklouseLiposcelis spp.A tiny, soft, pale insect that feeds on microscopic mold growing on paper, cardboard and stored food. It thrives in humid rooms and new construction.
Tell-tale sign: Very small, pale, wingless body. Risk: Booklice don't bite and aren't true lice; they indicate high humidity and mold.
Cellar Spider
Cellar SpiderPholcus phalangioidesA pale, delicate spider with extremely long, thin legs that hangs upside down in loose webs in basements and ceiling corners. When disturbed, it vibrates rapidly in its web.
Tell-tale sign: Tiny, peanut-shaped body with very long, hair-thin legs. Risk: Cellar spiders are harmless to people; the myth that they are deadly but can't bite is false.
Common House Spider
Common House SpiderParasteatoda tepidariorumA small, brownish spider that builds tangled cobwebs in corners, windows and basements. It is the web-builder most often seen inside North American homes.
Tell-tale sign: Round, mottled brown abdomen with chevron markings. Risk: Common house spiders are harmless and help catch flies and other indoor pests.
Crane Fly
Crane FlyTipula spp.A huge, fragile, long-legged fly often mistaken for a giant mosquito. Adults barely feed, and the larvae, called leatherjackets, eat grass roots.
Tell-tale sign: Extremely long, thin legs that detach easily. Risk: Crane flies cannot bite or sting and do not eat mosquitoes, despite the nickname mosquito hawk.
Eyed Click Beetle
Eyed Click BeetleAlaus oculatusA long, gray-and-black beetle with two large, eye-like spots on its thorax. When flipped over, it snaps a hinge on its body and launches itself into the air with an audible click.
Tell-tale sign: Two large black false eyespots ringed in white. Risk: Eyed click beetles are harmless; the eyespots are a bluff to scare predators.
Harvestman
HarvestmanOpiliones orderOften called daddy longlegs, a long-legged arachnid with a single fused, oval body and no venom glands. It scavenges on dead insects, fungi and plant matter.
Tell-tale sign: One round body section instead of two. Risk: Harvestmen have no venom and no silk; they are completely harmless.
Pill Bug
Pill BugArmadillidium vulgareA small land crustacean that rolls into a tight ball when disturbed, also called a roly-poly. It eats decaying plant matter in damp soil and mulch.
Tell-tale sign: Gray, armored, segmented body with seven pairs of legs. Risk: Pill bugs are harmless and only occasionally nibble seedlings.
Springtail
SpringtailCollembola classA tiny, wingless hexapod that jumps using a tail-like spring folded under its body. Springtails swarm in damp soil, potted plants and around leaks.
Tell-tale sign: Pinhead-size gray, white or black body. Risk: Springtails don't bite or damage homes; large numbers usually point to a moisture problem.
Which ones should you worry about?
7 of the 25 bugs in this guide can bite or sting. The ones to take seriously are American dog tick and mosquito. The rest are harmless or simply a nuisance.
Frequently asked questions
What is the most common one?
Among the bugs in this guide, the American dog tick and mosquito are the ones people ask about most.
Which of these are dangerous?
American Dog Tick and Mosquito can be medically significant.
How can I identify a bug I found?
Use the free bug identifier tool: choose the number of legs, wings, main color, size and where you found it, and it will list the closest matches.