Tiger (Linothele fallax)

Physical description and identification

The tiger spider is a medium-sized member of the curtain-web spiders, the family Dipluridae. It is a mygalomorph, meaning it belongs to the same ancient branch of the spider tree as tarantulas and purseweb spiders: the fangs swing downward in parallel rather than pinching together sideways, and the animal is built low, heavy and deliberate.

Adults

• Size: body length is commonly quoted at about 15 mm, but well-fed adult females frequently run to 20–25 mm, and the long legs carry the total span to roughly 50–70 mm. Males are slimmer and shorter-bodied with noticeably longer legs. This is a spider you can cover with a matchbox, not a hand.
• Colour: the carapace is glossy chestnut to near-black. The abdomen is dark chocolate brown with a series of paler brown to orange transverse bars running across the upper surface — the "tiger" pattern.
• Spinnerets: the single best field mark. The posterior lateral spinnerets are long, obviously segmented and project backwards past the end of the abdomen like a pair of small tails.
• Eyes: eight small eyes packed tightly together on a raised mound at the front of the carapace. Vision is poor; the spider hunts almost entirely by vibration, which is why the web matters more than the eyes.

Eggs

Mated females produce a rounded silk egg sac that stays deep inside the retreat rather than out on the curtain. The female remains with it and will repair or move it if the tunnel is disturbed. Across the genus the sac is white, lens-shaped or globular and holds a few dozen to a few hundred eggs.

Spiderlings

Hatchlings are almost uniformly dark and lack the banding, which is why photographs of juveniles look like a different animal. They remain inside the mother's web system for a period after the first moult, extending small side tunnels of their own from the edge of her sheet, then disperse on foot. The banded pattern appears gradually over several moults, and growth continues for years — mygalomorphs keep moulting after reaching maturity in the case of females.

The web

Dipluridae are called curtain-web spiders for a reason, and the common description of a "messy funnel web" undersells what this spider actually builds. It lays down a broad, irregular sheet of dry silk across the face of a crevice, a rotten log, a bank or a gap between buttress roots, then runs a tubular retreat back from that sheet into the dark. The sheet is the trap: an insect landing or walking on it loses its footing in the loose upper threads, and the vibration travels straight down the tunnel. The spider rushes out, strikes downward with its fangs, and carries the prey back inside. Our guide to spider webs covers how sheet-and-tunnel systems like this differ from orb webs and from the flat funnels of the unrelated funnel weavers.

Where the tiger spider lives

Linothele is a Neotropical genus. Its centre of diversity is the northern Andes and the humid forest that skirts it, with the largest number of described species in Colombia and Ecuador, and further species in Venezuela, Peru, Brazil and parts of Central America. Popular pages often flatten this to "a spider from Brazil"; that is too narrow for the genus and not the best description of L. fallax, whose living stock in collections is consistently traced to the Andean countries. The honest summary is that this is a South American forest spider of the humid northern tropics, not a Brazilian endemic.

The habitat requirement is simple and rigid: constant humidity, deep shade and a solid surface with a hole behind it. In practice that means the underside of fallen logs, cavities in rotten stumps, the space under loose bark, root buttresses, leaf litter packed against rock, and the shaded faces of earth banks along forest streams. The spider needs both an anchor for the sheet and a tunnel it can retreat into; remove either and it moves on. It does not colonise houses and is not a spider people meet indoors.

Are tiger spiders venomous?

Yes, in the ordinary sense that nearly every spider is venomous: Linothele fallax uses venom to immobilise insects. What matters for people is that the venom is not medically significant. There is no antivenom for any Linothele species because none has ever been needed, no death or serious envenomation has been attributed to the genus, and the species is widely kept by hobbyists without incident.

The confusion that surrounds this spider is purely a naming accident. The words "funnel web" attach to at least three unrelated groups: the harmless agelenid funnel weavers of gardens and lawns, the South American diplurids in this family, and the Australian funnel-web spiders of the family Atracidae — the genuinely dangerous animals that include the Sydney funnel-web. Only the Australian group has a venom (delta-hexatoxin) that attacks the human nervous system, and only that group warrants antivenom and emergency care.

Can tiger spiders bite?

They can, but it takes real provocation. The first response of a disturbed Linothele is to bolt down its tunnel; the second is to sprint away across the substrate. Bites happen almost exclusively when a spider is grabbed, pinned or handled.

Where a bite does occur, the recorded effects are local and brief: a sharp pain at the moment of the strike, comparable to a bee sting, with some redness and mild swelling that settles within a day or two. The fangs of a mygalomorph this size can produce two visible puncture marks, which looks alarming and accounts for a good deal of the fear attached to the group. There are no reports of systemic illness, tissue damage or lasting injury.

Sensible first aid is unremarkable: wash the site with soap and water, apply a cold pack for the pain and swelling, take a simple analgesic if needed, and keep the area clean while it heals. Seek medical advice if pain is severe or spreading, if the site shows signs of infection, or if you have any history of severe allergic reactions. If you can safely photograph the spider, do so — an identification is worth more to a clinician than a description. Do not apply heat, cuts, suction or any folk remedy.

Ecological importance and behavior of the tiger spider

The tiger spider is a sedentary, nocturnal ambush predator that may occupy the same log for years. By day it sits well back in the tunnel with its front legs resting on the silk. After dark it moves up to the entrance and waits. Prey is taken from the sheet rather than pursued: crickets, cockroaches, beetles, termites, ants and the occasional millipede or small amphibian that blunders onto the silk.

Natural predators: the source material for this species usually says predators are undocumented, but the pressures on a forest-floor mygalomorph are well understood. Spider-hunting wasps of the family Pompilidae specialise in paralysing burrowing spiders and dragging them to a nest; parasitoid flies, army ants, scolopendrid centipedes, coatis, small opossums, lizards and ground-foraging birds all take spiders of this size.

Prey–predator dynamics: a dense population of curtain webs removes a steady volume of litter-dwelling insects from a patch of forest floor, and in doing so occupies a layer that few other predators work.

Seasonal behaviour: in aseasonal tropical forest, activity continues year-round and breeding tracks rainfall rather than temperature. Mature males leave their webs to search, approach a female's sheet cautiously and drum on the silk to announce themselves before entering. Males die within months of maturing; females are long-lived by insect standards and can persist for several years, continuing to moult and to produce successive egg sacs.

Relationship with humans: minimal and benign in the wild. The species is well established in the invertebrate hobby, where a settled Linothele will fill an enclosure with silk in weeks. Wild collection for that trade and the clearance of humid forest are the only real human pressures on it.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species was described in the 1920s by Cândido Firmino de Mello-Leitão, the Brazilian zoologist who named more South American spiders than anyone before or since.
• "Tiger spider" is one of the most overloaded common names in arachnology. It is also applied to the Indian ornamental tarantulas of the genus Poecilotheria and to several striped orb weavers, which is a good argument for using Linothele fallax when precision matters.
• Dipluridae was carved up by a 2020 genomic study of the mygalomorphs, which moved several former diplurid groups into the resurrected families Ischnothelidae and Euagridae. Linothele stayed put, so the family is now a much tighter, mostly Neotropical group.

In summary, the tiger spider is a banded, long-spinneretted diplurid of humid South American forest that lives under a broad sheet of dry silk. It is venomous to insects and harmless to people, and the alarming reputation it sometimes inherits belongs entirely to a group of Australian spiders it is not related to.