naturebriefs
7:09in productionCh. 1 · Where it lives/ 7:09 · ceiling 15 min
Insects & invertebrates

Phoneutria nigriventer

A spider that walks into your house, raises its front legs like a boxer, and injects neurotoxins that scramble your nervous system—no web required.

Phoneutria nigriventer is a large, nocturnal spider native to the Southern Cone of South America—Brazil, Uruguay, Paraguay, and Argentina. It hunts by ambush at night. It hides under logs or in crevices by day. When threatened, it raises its first two pairs of legs. It inhabits forests, banana trees, foliage, and urban residences—including inside homes. Its venom contains PhTx3 peptides that act as broad-spectrum calcium channel blockers, inhibiting glutamate release and uptake. Its bite causes severe pain, tachycardia, priapism, and documented human deaths.

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Chapters & takeaways4
  1. 0:52
    Where it lives

    It lives where people live—in banana trees, foliage, and inside homes across the Southern Cone.

  2. 1:50
    How it behaves

    It hunts at night by ambush, hides by day, and warns with a raised-leg posture.

  3. 2:43
    What its venom does

    Its venom contains PhTx3 peptides that block calcium channels and disrupt glutamate signalling—causing pain, tachycardia, priapism, and documented deaths.

  4. 3:48
    How big it is

    It is large: up to 5 cm body length and 15 cm leg span.

Worth your time?

Yes. See the whole thing.

4.5/ 5
What works
  • ambush hunting at night
  • threat display via leg raising
  • neurotoxin delivery causing systemic human effects
What does not
  • build webs
  • hunt by day
  • avoid human dwellings
See it if
  • medical responders
  • field biologists
  • pest controllers
Skip it if
  • casual keepers
  • educators outside its range
  • anyone who assumes spiders stay outdoors
The written brief1 min read

What the species is and where it came from

Phoneutria nigriventer is a large, nocturnal spider native to the Southern Cone of South America—Brazil, Uruguay, Paraguay, and Argentina.

How it works, in terms someone would actually use

It hunts at night by ambush, not webs. It hides under logs or in crevices by day. When threatened, it raises its first two pairs of legs.

What it gets right

It gets right the balance of mobility, threat display, and venom potency for a ground-dwelling ambush predator in fragmented habitats—from forest floor to bedroom corner.

What it does not

It does not build webs. It does not hunt by day. It does not avoid human dwellings—it occupies them.

What it changed

It changed how clinicians assess envenomation in South America: its PhTx3 peptides are calcium channel blockers that inhibit glutamate release and uptake in neural synapses.

Who it is for, and who it is not

It is for medical responders, field biologists, pest controllers, and residents of southern Brazil, Uruguay, Paraguay, and Argentina. It is not for casual keepers, educators outside its range, or anyone who assumes spiders stay outdoors.

Is it worth your time

Yes—if you are in the Southern Cone and need to recognise a medically significant spider that enters homes, climbs banana trees, and delivers neurotoxic venom causing pain, tachycardia, priapism, or death.

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