Phoneutria boliviensis

Physical description and identification

Phoneutria boliviensis was described by the English arachnologist Frederick Octavius Pickard-Cambridge in 1897, originally in the genus Ctenus. With its twin P. depilata it is the smallest and most lightly built of the Brazilian wandering spiders, and the one whose limits have moved most recently: a 2021 study using both DNA and genital morphology showed that the animals living west of the Andes and north through Central America are a separate species, P. depilata. What remains under the name boliviensis is a cis-Andean spider of the Amazon and Orinoco basins.

Adults

• Size: females have a body length of roughly 30–40 mm and males 30–35 mm, with a leg span usually under 10 cm. That is noticeably smaller than P. fera or P. nigriventer.
• Colour: the sexes differ. Males are a fairly uniform brown with the abdomen a shade deeper than the carapace; females are yellowish to light brown and carry a distinctly yellow opisthosoma, the field mark most people notice first.
• Eyes: eight, in the ctenid 2-4-2 pattern — two small eyes low in front, a row of four above them and two set back at the sides.
• Distinctive features: long legs carrying paired spines at the joints, and a covering of fine hairs, or setae, over the carapace and abdomen. The cheliceral hairs are darker and far less conspicuous than the red brush of the larger species.
• Threat posture: like every member of the genus, a cornered individual rears back on its hind legs and lifts the first two pairs of legs high and spread. It is a warning display, not a prelude to an attack.

Eggs and egg sacs

A mated female may build up to four egg sacs in succession, each a flattened silk parcel she guards in a rolled leaf or crevice. Across those sacs a single female can produce several hundred to more than a thousand young. The best figures available — roughly 430 to 1,300 spiderlings per female and 28 to 34 days of incubation — come from Colombian field studies of populations now assigned to P. depilata, so they are a good guide rather than a measurement of this species.

Spiderlings

The young emerge as pale miniatures of the adults, already able to perform the raised-leg display, and disperse from the sac within days. They mature over about a year through a long series of moults; our guide to the spider life cycle explains the stages.

Hunting instead of a web

This is an ambush hunter that builds no capture web. It spends the day in leaf litter, under bark or inside rolled leaves and bromeliads, and forages at night over the ground and low vegetation, detecting prey by touch and vibration. Studies of stomach contents and field observations show a diet dominated by insects — crickets, cockroaches, moths and beetles — plus other spiders, with small frogs and lizards taken only occasionally. The older claim that it lives on frogs, lizards and mice overstates the vertebrate share considerably.

Where Phoneutria boliviensis lives

After the 2021 revision, P. boliviensis is a spider of the lowlands east of the Andes: Bolivia, Amazonian Peru, eastern Ecuador, Amazonian and Orinoco Colombia, southern Venezuela and western Brazil. Records from Costa Rica, Panama and the Pacific side of Colombia belong to P. depilata and should no longer be listed here.

Within that range it uses both humid and seasonally dry tropical forest, along with plantations, secondary growth and forest edges. Typical daytime shelters are leaf litter, fallen logs, loose bark, banana crowns and bromeliads; at night it climbs low vegetation to hunt. Like the rest of the genus it copes well with disturbed ground, so it turns up in rural buildings, woodpiles and stored produce — the reason most people ever meet one.

Is Phoneutria boliviensis venomous?

Yes. It belongs to a genus whose venom is genuinely medically significant, and its venom contains the same broad families of neurotoxic peptides — the PhTx fractions that act on voltage-gated sodium and calcium channels in nerve endings. In practice, though, this is the mildest member of the group. Comparative work shows lower potency than P. nigriventer, and the clinical picture reported from its range is dominated by local effects rather than the whole-body envenomation syndrome that species can cause.

Put that in context. Across the genus, Brazilian hospital series find that around nine in ten wandering spider bites produce local pain alone, under one in ten cause systemic signs and well below one per cent are severe, almost entirely in small children. For P. boliviensis the severe end of that scale is rarer still, and no confirmed death has been attributed to the species. The antiarachnid antivenom produced by the Instituto Butantan in Brazil covers Phoneutria envenomation, but it is seldom needed for this spider. See our comparison of the most venomous spiders for where the genus sits overall.

Bites: symptoms, timeline and what to do

Bites are defensive and uncommon. They happen when the spider is trapped against skin — inside a boot or a glove, under a hand reaching into firewood, or against a body in bedding. It does not chase people, and its first response to disturbance is the threat display rather than a bite.

Typical timeline. Most people describe an immediate sharp pinch followed by burning pain at the site, with redness and local swelling (oedema) over the next minutes to hours. In the great majority of cases nothing further happens and the pain fades within a day. A minority of patients develop systemic signs: sweating, nausea and vomiting, a racing heartbeat, tremor, anxiety and, rarely, changes in blood pressure or heart rhythm. Priapism, characteristic of severe envenomation by the larger species, is not a typical feature here.

What to do. Treat it as a medical matter, not a home-remedy one. Wash the site with soap and water, keep the limb still and the person calm, and go to a hospital or clinic for assessment — without delay if the patient is a child, elderly or pregnant, or if any symptom spreads beyond the bite. A cold pack over a cloth helps the local swelling on the way. Photograph the spider or bring it safely in a sealed container, because identification changes what doctors expect. Do not apply a tourniquet, cut the wound, suck it, or give alcohol.

Ecological importance and behavior of Phoneutria boliviensis

This is a solitary nocturnal predator that hunts on foot, which makes it an efficient control on crawling insects that no web would catch — cockroaches, crickets and beetles in particular. It is also prey, and that two-way role is its main ecological value.

Natural predators: spider wasps paralyse adults to stock their nests, and birds, small mammals, lizards, snakes and larger spiders all take them. Ants and parasitoid wasps attack the egg sacs, which is why females guard them so closely.

Prey-predator dynamics: the raised-leg display, the speed and the venom are all defences against those predators rather than weapons aimed at people. Spiders meter venom carefully, and a defensive bite often delivers very little of it — one reason so many bites amount to local pain alone.

Reproduction and season: courtship involves the male drumming and vibrating before approaching, and females are receptive more than once, producing a series of egg sacs over the season. Activity peaks in the wetter months in the more seasonal parts of the range. Adults live roughly one to two years.

Relationship with humans: mostly harmless coexistence. The spider avoids people, and the simple precautions — shaking out boots and clothing, using gloves in woodpiles and banana crowns, and carrying a torch at night — remove nearly all the risk.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The species name comes from Bolivia, where the first specimens were collected, even though the spider ranges across several countries.
• Its describer, F. O. Pickard-Cambridge, was the nephew of Octavius Pickard-Cambridge, another leading arachnologist — a rare case of two generations of one family naming spiders.
• Splitting P. depilata off in 2021 raised the number of recognised Phoneutria species from eight to nine.
• Mating does not always end badly for the male: females sometimes cannibalise their partner and sometimes let him walk away. The behaviour was documented in Colombian populations now assigned to P. depilata, so it is a close guide rather than a record for this species.

In summary, Phoneutria boliviensis is the mild member of a fearsome genus: a small, yellow-bellied night hunter whose bite usually amounts to sharp local pain and swelling. It still deserves a doctor's assessment and a wide berth, but not the reputation its larger cousins have earned.