Pirate Spider Identification Guide
Identify a pirate spider by its spiny legs, humped abdomen, and habit of lurking at the edge of other spiders' webs.
Read the full Pirate Spider encyclopedia entry →
Key Visual Features
Pirate spiders are small, specialized hunters that invade the webs of other spiders rather than building elaborate webs of their own.
- Size: Body length typically 3-6 mm, quite small compared to many web-building spiders.
- Color: Pale tan to brown, often with darker patterning or spots on the abdomen, and legs banded in alternating light and dark tones.
- Body shape: Distinctive humped or raised abdomen that sits higher than the cephalothorax, giving the spider an unusual silhouette compared to most other small spiders.
- Eyes: Eight eyes arranged in two rows across the front of the head.
- Legs: Eight legs bearing noticeably stout spines, particularly on the front pairs, an adaptation used for gripping and immobilizing other spiders during an attack.
- Web: Pirate spiders build only a minimal, simple web of their own, if any, and are much more often found sitting motionless at the edge of another spider's web rather than in a web of their own construction.
Where and When You'd See It
Pirate spiders are found in gardens, woodlands, and grassy habitats wherever other web-building spiders are present, since they depend on those webs for hunting. Look for them at the margins of orb webs, sheet webs, or tangle webs, often sitting very still for long periods. They are active during the day and night depending on the activity patterns of the host spiders they are targeting.
Similar-Looking Bugs
- Small orb weavers or sheet-web spiders: Could be confused at a glance, but lack the humped abdomen and heavily spined front legs of a pirate spider.
- Cobweb spiders: Some have a similarly rounded abdomen, but do not show the same raised hump or spiny leg armament.
- Crab spiders: Also ambush other prey, but have a flattened body and sideways-held front legs rather than a humped abdomen.
Quick ID Checklist
- Small size with a distinctly humped, raised abdomen
- Stout spines on the front legs used for gripping prey
- Pale tan to brown coloring with banded legs
- Found sitting motionless at the edge of another spider's web
- Builds little to no web of its own
Behavior Notes
This spider approaches another spider's web with slow, careful movements, plucking the silk to mimic the vibrations of trapped prey, then seizes the web's owner using its spined front legs when it comes to investigate.
Frequently asked questions
What body feature helps identify a pirate spider?
A distinctly humped, raised abdomen that sits higher than the cephalothorax, along with noticeably spiny front legs.
Where is the best place to look for a pirate spider?
At the edges of other spiders' webs — orb webs, sheet webs, or tangle webs — since pirate spiders rely on these webs rather than building elaborate webs of their own.
Does a pirate spider build its own web?
It builds only a minimal web at most, and is far more commonly found stationed at the margin of another spider's web.
How can I tell a pirate spider from a small orb weaver sitting on a web?
Check the abdomen shape and legs — pirate spiders have a raised hump on the abdomen and stout spines on the front legs, features typical orb weavers lack.