A Field Guide to the
Spiders of California

Identification at a glance

Spiders of the World Araneae · Order of the Web Compiled from iNaturalist, BugGuide, Essig Museum

California has over a thousand spider species across fifty-four families, but these fifteen account for roughly 90% of what you'll encounter. Eye arrangement settles most families on its own; silhouette, hunting style, habitat, and web architecture handle the rest. Only two groups — the widows and the recluses — have venom worth treating as a medical concern, and recluses are functionally absent from most of the state.

I. Eye-Arrangement Key

§ Primary Diagnostic

Spider eyes are arranged in family-specific geometries. View from directly in front. Count the rows, note relative sizes, look for tight clusters or pairs.

Salticidae
jumpers
Lycosidae
wolves
Mygalomorphs
tight tubercle
Oxyopidae
lynx hexagon
Dysderidae
6 in tight oval
Sicariidae
3 pairs (diads)
Araneidae
laterals set apart
Generalized 4-4
many families

II. Size at a Glance

§ Body Length, Female, Typical
Scale · millimetres, body only (legs excluded) · linear
0 5 10 15 20 30 40 50 60+ mm Salticidae (jumpers) · 4–15 Theridiidae (widows) · 3–15 Araneidae (orb weavers) · 5–25 Lycosidae (wolves) · 10–30 Pholcidae (cellar) · 2–10 body, legs 2×+ Zoropsidae · 10–20 Nemesiidae (Calisoga) · 15–30 Theraphosidae (tarantula) · 40–70 →

III. The Fifteen Families

§ Bay Area · Statewide
Family 01 / 15
Headlight AME
4–2–2 rows
Leap Hunter

Salticidae

Jumping Spiders

Quick ID Tell Two huge forward-facing eyes like car headlights on a stocky, short-legged body. Often turn to face you. If it watches you back, it's a jumper.
Size
4–15 mm body; some Phidippus to 22 mm
Hunting Style
Active diurnal hunter. No snare web. Drags a silk dragline while stalking.
Habitat
Sun-warmed walls, fences, leaves, windowsills. Everywhere.
Body
Boxy cephalothorax, short strong legs, often iridescent scales or bright patches.
Top California Species
salticidae plate
Plate 01 — Salticidae
Reference photos: iNaturalist · Salticidae
Family 02 / 15
8 equal eyes
2 rows of 4
Cobweb · Gum Threads

Theridiidae Medical

Cobweb Spiders · Widows · False Widows

Quick ID Tell Glossy, globe-shaped abdomen much larger than the head, hanging upside down in a messy tangle web. Comb of serrated bristles on hind tarsi (rarely visible without a lens).
Size
3–15 mm. Mature female black widow: 8–13 mm body, much bigger than male.
Web Type
Irregular cobweb, no ordered geometry. Sticky gum-footed threads anchor to ground/surface.
Habitat
Sheds, undersides of furniture, woodpiles, rock crevices, garage corners.
Body
Legs long and thin; abdomen dominant and often glossy. Widows have red hourglass ventral.
Top California Species
theridiidae plate
Plate 02 — Theridiidae
Reference photos: iNaturalist · Theridiidae
Family 03 / 15
Laterals small,
widely separated
Orb Web

Araneidae

Orb Weavers

Quick ID Tell Geometric wheel-and-spoke web hung in open air. Spider sits head-down in the center or hides in a nearby leaf retreat. Abdomen usually bulbous, often patterned.
Size
5–25 mm. Females much larger than males.
Web Type
Vertical orb with radial spokes and spiral sticky thread. Often rebuilt nightly.
Habitat
Between shrubs, eaves, fences, garden gaps. Nocturnal activity, diurnal retreat.
Body
Abdomen larger than cephalothorax, often with dorsal markings (folium). Eight legs held in X or spread on web.
Top California Species
araneidae plate
Plate 03 — Araneidae
Reference photos: iNaturalist · Araneidae
Family 04 / 15
4–2–2
Huge PME pair
Ground Runner

Lycosidae

Wolf Spiders

Quick ID Tell Large ground spider with two oversized eyes staring straight up at you from a row of four small eyes. Eyeshine at night (reflective tapetum). Females carry egg sacs attached to spinnerets.
Size
10–30 mm body.
Hunting Style
Nocturnal active hunter on the ground. Some build burrows with silk-lined entrances.
Habitat
Leaf litter, under rocks, lawns, trail edges. Enter homes in fall.
Body
Drab brown/gray longitudinal stripes. Legs long, muscular, sprinter's build. Mothers carry spiderlings on back.
Top California Species
lycosidae plate
Plate 04 — Lycosidae
Reference photos: iNaturalist · Lycosidae
Family 05 / 15
8 equal
rear row recurved
Sheet + Funnel

Agelenidae

Funnel Weavers

Quick ID Tell Flat sheet web ending in a tubular funnel retreat. Spider waits just inside the funnel, ready to charge out. Two prominent posterior spinnerets protrude past the abdomen.
Size
6–20 mm body.
Web Type
Horizontal sheet plus funnel retreat. Non-sticky; relies on speed.
Habitat
Corners of ground-level vegetation, rock piles, under eaves, tall grass.
Body
Brown longitudinal markings; cephalothorax often with darker band. Legs long.
Top California Species
agelenidae plate
Plate 05 — Agelenidae
Reference photos: iNaturalist · Agelenidae
Family 06 / 15
3-2-3 triad pattern
Corner Tangle

Pholcidae

Cellar Spiders · "Daddy Long-Legs"

Quick ID Tell Tiny pale body with legs four to five times longer. Hangs inverted in a loose mess of web in a basement corner. Vibrates body wildly when disturbed (whirling defense).
Size
2–10 mm body; leg span to 50 mm.
Web Type
Tangled, irregular, non-sticky. Catches prey including other spiders.
Habitat
Ceilings, cellars, garages, crawl spaces, vegetation in southern CA.
Body
Pale gray/tan. Abdomen elongate in Pholcus, globular in Holocnemus.
Top California Species
pholcidae plate
Plate 06 — Pholcidae
Reference photos: iNaturalist · Pholcidae
Family 07 / 15
All small, recurved
often on tubercles
Flower Ambush

Thomisidae

Crab Spiders

Quick ID Tell First two pairs of legs enormously longer than the back two, held sideways like crab claws. Walks sideways. Often sits motionless on a flower.
Size
4–10 mm body.
Hunting Style
Ambush on flowers. Many species can change color (yellow ↔ white) over days.
Habitat
Petals, flower heads, foliage. Spring through fall.
Body
Abdomen wider than long in some genera, angular shoulders.
Top California Species
thomisidae plate
Plate 07 — Thomisidae
Reference photos: iNaturalist · Thomisidae
Family 08 / 15
Tight cluster on
ocular tubercle
Burrow

Theraphosidae

Tarantulas

Quick ID Tell Very large, hairy, with fangs that strike downward (not sideways). Walks with a distinctive "ambling" gait. In CA, almost always Aphonopelma. Males wander in late summer / early fall looking for mates.
Size
Body 40–70 mm. Leg span to 15 cm.
Hunting Style
Burrow-dwelling ambush predator. Fangs parallel (orthognathous), strike downward.
Habitat
Grasslands and oak woodland of inland CA; Central Valley, Diablo Range, foothills. Not typical in coastal Bay Area.
Body
Uniformly hairy, usually black or brown, legs thick. Urticating hairs kicked from abdomen in defense.
Top California Species
theraphosidae plate
Plate 08 — Theraphosidae
Reference photos: iNaturalist · Theraphosidae
Family 09 / 15
Tight tubercle
(tarantula-like)
Burrow + Silk Sheet

Nemesiidae

Calisoga · "False Tarantula"

Quick ID Tell Looks like a small tarantula but smaller, less shaggy, and distinctly more active/aggressive. Builds silk-lined burrow with sheet web at entrance. Extremely common in Oakland and East Bay hills — the "tarantula" most people in the Bay Area see is almost always this.
Size
15–30 mm body. Legs robust but not as thick as tarantulas.
Hunting Style
Burrow with entrance webbing; ambushes passing prey. Mygalomorph (orthognathous fangs).
Habitat
Coast Range hills, oak woodland, grassy slopes. Oakland hills especially abundant.
Body
Brown to reddish-brown. Less uniformly hairy than tarantula. Males wander in fall.
Top California Species
nemesiidae plate
Plate 09 — Nemesiidae
Reference photos: iNaturalist · Nemesiidae
Family 10 / 15
8 in 2 rows,
posterior recurved
Wall Hunter

Zoropsidae

False Wolf Spiders

Quick ID Tell Looks like a wolf spider on the wall of your house. Mediterranean invader now common throughout Bay Area homes. Cribellate (uses hackled silk); legs stouter and body flatter than Lycosidae.
Size
10–20 mm body.
Hunting Style
Active nocturnal hunter. Lays patches of cribellate silk near resting spots.
Habitat
Inside walls, behind furniture, basements, garages. Less often outdoors in CA.
Body
Mottled brown with chevron or banding on abdomen. Eyes small, even — no wolf-spider giants.
Top California Species
zoropsidae plate
Plate 10 — Zoropsidae
Reference photos: iNaturalist · Zoropsidae
Family 11 / 15
Hexagon of 6
+ 2 tiny below
Foliage Hunter

Oxyopidae

Lynx Spiders

Quick ID Tell Slender green or pale spider on foliage with obvious black spines sticking out from the legs. Six eyes in a hexagon on the front of the head. Leaps after prey like a small jumper.
Size
8–18 mm body.
Hunting Style
Active diurnal hunter on plants; leaps on prey. No snare web.
Habitat
Foliage, chaparral, gardens. Often bright green (Peucetia) on leaves.
Body
Abdomen tapered to a point; legs with prominent black spines set at angles.
Top California Species
oxyopidae plate
Plate 11 — Oxyopidae
Reference photos: iNaturalist · Oxyopidae
Family 12 / 15
6 eyes in tight oval
Isopod Specialist

Dysderidae

Sow Bug Killer · Woodlouse Spider

Quick ID Tell Striking: dark red-orange cephalothorax and legs, pale pink-gray abdomen, six eyes in a tight oval, chelicerae that project forward like curved tusks. Hunts sow bugs specifically. Found under bricks and flowerpots.
Size
9–15 mm body.
Hunting Style
Nocturnal ground hunter. Enlarged fangs pierce sow bug armor. Defensive bite possible but minor.
Habitat
Damp gardens, under stones, compost, wood. European introduction, widespread in CA.
Body
Bicolored — rust front, pale back. No web (except for small silk resting sac).
Top California Species
  • Dysdera crocata — Only species typically seen; introduced, cosmopolitan
dysderidae plate
Plate 12 — Dysderidae
Reference photos: iNaturalist · Dysderidae
Family 13 / 15
PME oval & silvery
Silk Retreat

Gnaphosidae

Ground Spiders

Quick ID Tell Fast-moving, flattened, often uniformly dark ground spider. Look for distinctly cylindrical, wide-spaced spinnerets sticking out the back end — visible even without magnification. Posterior median eyes often flattened, oval, or silvery.
Size
3–15 mm body.
Hunting Style
Nocturnal active hunter. Silk retreat sac under rocks or bark.
Habitat
Ground, under rocks, logs, leaf litter. Sometimes enter homes.
Body
Elongated. Cephalothorax oval, abdomen often a single matte color.
Top California Species
gnaphosidae plate
Plate 13 — Gnaphosidae
Reference photos: iNaturalist · Gnaphosidae
Family 14 / 15
8 small equal eyes
Sheet + Knockdown

Linyphiidae

Sheet Weavers · Money Spiders · Dwarf Spiders

Quick ID Tell Very small spider (often 2–3 mm) hanging upside down beneath a horizontal or domed sheet web strung in low vegetation. Morning dew in a lawn reveals dozens of these webs at once.
Size
1–7 mm body. Most are under 3 mm.
Web Type
Horizontal sheet with tangled "knock-down" threads above. Prey fall onto sheet from flight lines.
Habitat
Low vegetation, grass, mulch, shrubs. Dewy lawns in fall show them best.
Body
Often dark with faint patterns. Many species ride silk threads on wind (ballooning).
Top California Genera
  • Neriene litigiosa — Sierra Dome, huge conspicuous dome webs in shrubs
  • Frontinella — Bowl and doily, two-tier web architecture
  • Erigone and relatives — Tiny, often ballooning, ubiquitous
linyphiidae plate
Plate 14 — Linyphiidae
Reference photos: iNaturalist · Linyphiidae
Family 15 / 15
6 eyes in 3 pairs
Silk Mat · Crevice

Sicariidae Medical

Recluse Spiders

Quick ID Tell Drab tan, flattened body, long thin legs — but the diagnostic is six eyes arranged in three pairs (not eight). A dark violin shape may sit on the cephalothorax, pointing backward. Essential caveat: the brown recluse (L. reclusa) does not live in California. CA has native desert recluses, but they are rare and desert-restricted.
Size
6–12 mm body.
Hunting Style
Nocturnal active hunter. Retreats to irregular silk mat by day.
Habitat
In CA, desert shelters: rocks, crevices, abandoned burrows. Not in Bay Area homes.
Reputation
Overdiagnosed. Nearly all "recluse bites" in CA are misattributed: Staphylococcus infections, other spiders, or unknown causes.
Top California Species
sicariidae plate
Plate 15 — Sicariidae
Reference photos: iNaturalist · Sicariidae

IV. Confusion Matrix

§ The Pairs That Fool Everyone
Pair Why the confusion Diagnostic Tell
Calisoga vs. Aphonopelma
(Nemesiidae vs. Theraphosidae)		 Both are mygalomorphs with tight eye clusters and burrow habits. Calisoga is the "tarantula" almost everyone reports in the Bay Area. Size + hair. True tarantulas exceed 40 mm body with uniformly dense "pelt" hair; Calisoga rarely exceeds 30 mm and is sparsely haired with shiny chitin showing.
Steatoda grossa vs. Latrodectus hesperus
(false widow vs. black widow)		 Both glossy, globose, hang in messy webs in the same habitats. Both bite. Ventral mark. Mature female L. hesperus has a bright red hourglass underneath. S. grossa has no hourglass; purplish-brown body often with pale dorsal markings; red is absent.
Zoropsis spinimana vs. wolf spider
(Zoropsidae vs. Lycosidae)		 Both brown, striped, ground-runner body plan. Both found indoors in fall. Eye pattern. Wolf spiders have two huge posterior median eyes dominating the face; Zoropsis has eight small, roughly equal eyes. Also, wolves prefer outdoors and leaf litter; Zoropsis owns your walls.
Pholcidae vs. Opiliones
(cellar spider vs. harvestman / "daddy long-legs")		 Both called "daddy long-legs." Long thin legs, small body. Body segments. Opiliones have one fused oval body segment (no waist); Pholcidae have the classic two-segment spider body (cephalothorax + abdomen separated by a narrow pedicel). Pholcidae build webs; Opiliones never do.
Lycosidae vs. Pisauridae
(wolf vs. nursery-web)		 Both large, outdoor, fast ground-runners with striped bodies. Less of an issue in CA (Pisauridae sparse) but worth knowing for Phase 2. Egg sac carry. Wolf spider females carry egg sac attached to spinnerets (dragged behind); nursery-web females carry it in their jaws (held under body).
Gnaphosidae vs. Clubionidae / Miturgidae
(ground spiders vs. sac spiders)		 Both elongate, hunting (no web), found in similar places. Sac spiders (Cheiracanthium) are common house spiders. Spinnerets and PME. Gnaphosidae have cylindrical, widely spaced spinnerets protruding noticeably; their PME are often flattened or silvery. Sac spiders have short conical spinnerets and uniformly round dark eyes.
Loxosceles vs. any brown hunter
(recluse false alarms)		 Any brown spider of moderate size gets called "recluse." Essentially every non-Loxosceles brown spider is misidentified this way at some point. Count eyes. Six eyes in three pairs = recluse. Eight eyes = not a recluse, no matter what the violin mark looks like. Also, recluses do not live in coastal CA.
Salticidae vs. Thomisidae
(jumper vs. crab)		 Both small, diurnal, sit on flowers and foliage, don't build webs. Posture and eyes. Jumpers have two huge anterior median eyes and short legs held close. Crab spiders have all small eyes (sometimes on turrets) and the front two leg pairs much longer and held sideways.
Araneidae vs. Tetragnathidae
(orb weavers vs. long-jawed orb weavers)		 Both build orb webs. Body shape and web orientation. Araneidae have bulky, often humped abdomens and vertical webs. Tetragnathidae are elongate (sometimes resembling sticks) with horizontal webs, often near water; their chelicerae are enlarged.
Pholcidae vs. Theridiidae
(cellar spider vs. cobweb/widow in dim light)		 Both hang inverted in irregular webs in dark corners. Proportion. Pholcidae have pencil-thin legs several times longer than a tiny body. Theridiidae have moderately long legs on a globose body where the abdomen is the dominant feature.

V. Field Technique

§ How to Read a Spider

01 · THE TWO-SECOND SCAN
Before anything else: web or no web? If web, what shape? Orb, cobweb, funnel, sheet, none? That alone cuts the family list in half.

02 · EYES BEFORE COLOR
Colors vary; eye geometry doesn't. A handheld macro lens on a phone brings eye arrangement within easy reach in most light. Count rows, note relative sizes, look for tight clusters or obvious pairs.

03 · PROPORTIONS OVER MARKINGS
Leg length relative to body, abdomen size relative to cephalothorax, whether legs are held tucked, splayed, or crab-wise. These stay constant across individuals; markings vary wildly.

04 · CONTEXT IS A CLUE
Where you found it narrows the list before you look at the spider. Inside on a wall vs. garden vs. under a rock vs. in a dewy lawn all implicate different families.

05 · POST TO iNATURALIST
Even uncertain IDs get corrected by specialists within hours. Every submission sharpens the mental library and contributes to the very dataset used to build this guide.

This is Volume I of a concentric expansion: California first, then the rest of the United States, then Australia, Costa Rica, and India, then the world. Every subsequent volume extends the same template. Families compared across regions reveal the patterns that matter.

Set in Fraunces, Spectral & JetBrains Mono · Compiled 2026 · Phase I of IV