Spider families of North America
Family-level reference for the spider families occurring north of Mexico. Each entry covers diagnostic characters, web architecture, hunting strategy, medical significance, and the families most often confused with it.
| Family | Common name | Species (Nearctic) | Web type | Medical significance |
|---|---|---|---|---|
| Theridiidae | Cobweb weavers and widow spiders | approximately 250 species north of Mexico | Irregular three-dimensional tangle web, frequently with gumfooted anchor lines running to the substrate | The genus Latrodectus is the only medically significant group in the family |
| Sicariidae | Recluse and six-eyed sand spiders | 13 species north of Mexico, 11 of them native to the Southwest | Irregular sheet of loose, adhesive-free silk used as a retreat rather than a snare | High |
| Lycosidae | Wolf spiders | approximately 240 species north of Mexico | None for prey capture | Low |
| Salticidae | Jumping spiders | approximately 315 species north of Mexico | None for prey capture | Low |
| Araneidae | Orb weavers | approximately 180 species north of Mexico | Vertical orb web with radial spokes and a viscid capture spiral, usually rebuilt daily | Low |
| Agelenidae | Funnel weavers and grass spiders | approximately 100 species north of Mexico | Horizontal non-adhesive sheet with a funnel-shaped retreat at one edge | Low |
| Pholcidae | Cellar spiders and daddy long-legs spiders | approximately 34 species north of Mexico, several of them introduced synanthropes | Loose, irregular, non-adhesive tangle in a ceiling corner or void | None documented |
| Thomisidae | Crab spiders | approximately 130 species north of Mexico | None | None of consequence |
| Cheiracanthiidae | Yellow sac spiders | approximately 10 species north of Mexico, the most common ones introduced | No capture web | Low to moderate |
| Gnaphosidae | Ground spiders | approximately 255 species north of Mexico | None for capture | Low |
| Tetragnathidae | Long-jawed orb weavers | approximately 55 species north of Mexico | Orb web with an open hub, usually horizontal or inclined and with relatively few radii | None documented |
| Linyphiidae | Sheet weavers and money spiders | approximately 950 species north of Mexico, the largest family in the Nearctic fauna | Horizontal sheet, dome, or bowl-and-doily with a tangle of stopping threads above | None |
| Pisauridae | Nursery web and fishing spiders | approximately 15 species north of Mexico | None for capture | Low |
| Sparassidae | Huntsman and giant crab spiders | approximately 10 species north of Mexico, several introduced and restricted to warm regions | None | Low |
| Theraphosidae | Tarantulas | approximately 55 Aphonopelma species north of Mexico, confined to the Southwest and southern plains | Silk-lined burrow with a collar of silk at the entrance | Very low |
| Corinnidae | Antmimic and dark sac spiders | approximately 45 species north of Mexico | None | Low |
| Oxyopidae | Lynx spiders | approximately 18 species north of Mexico | None | Low |
| Uloboridae | Hackled orb weavers and feather-legged spiders | approximately 15 species north of Mexico | Horizontal orb, partial orb, or reduced single-line web of cribellate silk | None |
| Filistatidae | Crevice weavers | approximately 8 species north of Mexico, mainly in the South and Southwest | Cribellate silk radiating from a tubular crevice retreat | None documented |
- 6 profiled species
Theridiidae
Cobweb weavers and widow spidersTheridiidae is the family that contains every widow spider in North America, along with the small cobweb spiders found in the corners of nearly every building on the continent. Family members share a comb of serrated bristles on the fourth tarsus used to fling silk over prey, and they build irregular three-dimensional tangle webs rather than the geometric orbs of Araneidae.
- 2 profiled species
Sicariidae
Recluse and six-eyed sand spidersSicariidae contains the recluse spiders of the genus Loxosceles, the only spiders in North America whose venom is established as capable of producing dermonecrotic lesions. The family is defined by six eyes arranged in three widely separated pairs, a character that separates it immediately from nearly every spider it is mistaken for.
- 1 profiled species
Lycosidae
Wolf spidersWolf spiders are robust, fast, ground-dwelling hunters that capture prey by pursuit rather than by web. The family is recognized by a distinctive eye arrangement of four small eyes in a bottom row, two very large forward-facing eyes above them, and two more on top of the carapace, and by the female's habit of carrying her egg sac attached to the spinnerets.
- 1 profiled species
Salticidae
Jumping spidersSalticidae is the largest family of spiders in the world and the most visually sophisticated. Jumping spiders hunt by sight using enormous forward-facing anterior median eyes with a movable retina, and they capture prey by calculated leaps powered by hydraulic pressure rather than muscle extension in the legs.
- 3 profiled species
Araneidae
Orb weaversAraneidae builds the geometric wheel-shaped orb web that most people picture when they picture a spider web. The family includes the large, conspicuous garden spiders of late summer, the Joro spider now spreading through the Southeast, and hundreds of smaller species that rebuild their webs nightly.
- 3 profiled species
Agelenidae
Funnel weavers and grass spidersFunnel weavers build a flat, non-sticky sheet of silk with a tubular retreat at one edge, from which the spider rushes out to seize insects that stumble onto the sheet. The family includes the North American grass spiders of the genus Agelenopsis and the introduced hobo spider of the Pacific Northwest.
- 1 profiled species
Pholcidae
Cellar spiders and daddy long-legs spidersCellar spiders are the pale, extremely long-legged spiders that occupy basement and garage ceilings across North America. They build loose, untidy tangle webs, vibrate rapidly when disturbed, and are the subject of the most persistent false claim in popular spider folklore.
- 0 profiled species
Thomisidae
Crab spidersCrab spiders are flattened, laterigrade ambush predators that sit motionless on flowers and foliage and seize pollinators with greatly enlarged front legs. Several genera can change body color over a period of days to match the substrate they occupy.
- 1 profiled species
Cheiracanthiidae
Yellow sac spidersYellow sac spiders are small, pale nocturnal hunters that build a silken sleeping sac in wall and ceiling corners rather than a capture web. Cheiracanthium is one of the more frequent causes of verified indoor spider bites in North America, though the bites are mild.
- 0 profiled species
Gnaphosidae
Ground spidersGround spiders are dark, flattened, fast-moving nocturnal hunters found under stones, boards, and debris. The family is defined by cylindrical, widely separated anterior spinnerets, and includes the mouse spiders and parson spiders commonly found indoors at floor level.
- 0 profiled species
Tetragnathidae
Long-jawed orb weaversLong-jawed orb weavers build horizontal or steeply inclined orb webs, usually over water or in moist vegetation, and have strikingly elongated bodies and chelicerae. When disturbed they stretch their legs along a stem and become nearly invisible.
- 0 profiled species
Linyphiidae
Sheet weavers and money spidersLinyphiidae is the second-largest spider family in the world and by far the most abundant in temperate North America by individual count, yet it is almost entirely overlooked because most members are under three millimetres. They build horizontal sheet or bowl webs and hang upside down beneath them.
- 0 profiled species
Pisauridae
Nursery web and fishing spidersNursery web spiders resemble large wolf spiders but carry their egg sac in the chelicerae and build a silken nursery tent for the emerging spiderlings. The Dolomedes fishing spiders are semi-aquatic, hunting at the water surface and capable of taking small fish and tadpoles.
- 0 profiled species
Sparassidae
Huntsman and giant crab spidersHuntsman spiders are large, flattened, fast, laterigrade hunters adapted to living in narrow crevices under bark and in structures. In the United States the family is represented mainly by the introduced Heteropoda venatoria in the Gulf states and the native Olios in the Southwest.
- 0 profiled species
Theraphosidae
TarantulasTarantulas are the large-bodied mygalomorph spiders of the American Southwest, with downward-striking parallel fangs, long lifespans, and a defensive strategy based on flicking urticating hairs from the abdomen. Native United States species are docile and of negligible medical concern.
- 0 profiled species
Corinnidae
Antmimic and dark sac spidersCorinnids are small, glossy, fast-moving ground hunters, many of which mimic ants in both body form and behavior, raising the front legs to imitate antennae and walking in an erratic ant-like gait.
- 0 profiled species
Oxyopidae
Lynx spidersLynx spiders are agile, spiny-legged diurnal hunters that stalk and leap on prey among vegetation. The green lynx spider is a conspicuous bright green species of the southern United States and a significant predator in cotton and other row crops.
- 0 profiled species
Uloboridae
Hackled orb weavers and feather-legged spidersUloboridae is the only spider family in North America that has completely lost its venom glands. Members capture prey using cribellate silk, a dry hackled wool of nanofibres that entangles insects mechanically, and then subdue prey by wrapping it in silk until it is crushed.
- 1 profiled species
Filistatidae
Crevice weaversCrevice weavers build radiating mats of woolly cribellate silk spreading out from a hole in masonry, stucco, or rock. The southern house spider of the southern United States is the family's most familiar member, with dark bulky females and long-legged tan males often mistaken for recluses.