Field Guide / Ticks, Spiders & Biting Pests
The ticks, spiders, biting flies, and stinging insects people most often meet while hunting, fishing, camping, and hiking. Search by name, or filter by kind, health concern, and region.
Call 911 for trouble breathing, swelling of the face or throat, or dizziness after a sting or bite. This guide is general information, not medical advice. Photos are AI-generated and cannot replace a real look at the animal. If you are sick after a bite, especially with a fever or a spreading rash, see a doctor and mention the bite.
16 pests
TicksDermacentor variabilis
A large, common tick of grassy trails and field edges, easy to spot with its cream markings, and a carrier of Rocky Mountain spotted fever and tularemia.
Size: Unfed adult about 3/16 inch; swells to about 1/2 inch when fed
TicksIxodes scapularis
A tiny tick of eastern woods and brush, the main carrier of Lyme disease in the eastern United States, and easy to miss because the young ones are poppy-seed small.
Size: Nymph about a poppy seed; adult about a sesame seed
TicksAmblyomma americanum
An aggressive tick of the South and Midwest, recognized by the single white spot on the adult female, and linked to alpha-gal syndrome, a red-meat allergy.
Size: Adult female about 1/8 to 1/4 inch unfed
TicksDermacentor andersoni
A tick of the Rocky Mountain states, found in brush and grass at mid elevations, and a carrier of Colorado tick fever and Rocky Mountain spotted fever.
Size: Unfed adult about 3/16 inch
Spiders & ScorpionsCentruroides sculpturatus
A slender, pale scorpion of the Sonoran Desert, the most venomous scorpion in the United States, with a painful sting that is usually not dangerous to healthy adults.
Size: About 2 to 3 inches
Spiders & ScorpionsLatrodectus species
A shy, shiny black spider with a red hourglass underneath, found in woodpiles, sheds, and dark corners, with a neurotoxic bite that needs medical care.
Size: Female body about 1/2 inch, with a leg span of about 1.5 inches
Spiders & ScorpionsLoxosceles reclusa
A shy, light brown spider with a violin-shaped mark, native to the south-central United States, whose bite is often painless at first and sometimes leaves a slow-healing wound.
Size: Body about 1/4 to 1/2 inch, with a leg span of about an inch
Biting Flies & MitesCulicoides species
A tiny, nearly invisible biting fly of shorelines and marshes, common at dusk and dawn, with a surprisingly painful bite.
Size: About 1/16 inch
Biting Flies & MitesTrombiculidae (larvae)
A tiny mite larva of grass and brush that leaves intensely itchy red welts, usually around the ankles, waist, and other tight spots.
Size: About 1/150 inch, barely visible
Biting Flies & MitesChrysops species
A persistent, hard-biting fly of marshes, lakeshores, and wet woods, active on hot, sunny days, with a bite that slices skin and hurts.
Size: About 1/4 to 1/2 inch
Biting Flies & MitesCulicidae (family)
The most common biting insect outdoors, a nuisance at dusk and dawn near standing water, and a carrier of diseases such as West Nile virus.
Size: About 1/4 inch
Stinging InsectsDolichovespula maculata
A large black-and-white wasp that builds big gray papery nests in trees and on buildings and attacks anything that threatens the nest.
Size: About 3/4 inch
Stinging InsectsApis mellifera
A fuzzy, gentle, golden-brown bee that stings only to defend itself, and loses its barbed stinger and dies when it does.
Size: About 1/2 inch
Stinging InsectsPolistes species
A slim, long-legged wasp that builds an open, umbrella-shaped nest under eaves and ledges, and usually stings only when its nest is threatened.
Size: About 3/4 inch
Stinging InsectsSolenopsis invicta
A small, aggressive reddish ant of the South whose mounds erupt in a swarm when disturbed, and whose stings burn and blister.
Size: About 1/8 to 1/4 inch
Stinging InsectsVespula and Dolichovespula species
A bold, black-and-yellow wasp that nests in the ground and in walls and defends its nest fiercely, especially in late summer.
Size: About 3/8 to 5/8 inch