Phoneutria
Genus of venomous wandering spiders from South America.
Phoneutria is a genus of spiders in the family Ctenidae, primarily distributed across northern South America, with a single species extending into Central America. Commonly called Brazilian wandering spiders, they are also referred to as armed spiders or banana spiders, though the latter name is shared with other unrelated spiders. The genus was established by Maximilian Perty in 1833, with the name derived from the Greek word for "murderess." Perty originally placed two species in the genus, one of which, *Phoneutria fera*, serves as the type species. Members of this genus are distinguished from related genera like *Ctenus* by the presence of dense prolateral scopulae—a brush of fine hairs—on the pedipalp tibiae and tarsi in both sexes. They can be confused with non-medically significant ctenids, particularly *Cupiennius*, and the presence of red hairs on the chelicerae is an unreliable identifying feature, as some *Phoneutria* species lack them. More reliable indicators include a dark linear stripe on the frontal palps, a single thin black line running along the dorsal carapace, strong ventral markings on the legs with contrasting dark mid-segments and lighter joints, and a ventral abdomen pattern of several rows of black dots or an overall reddish color. Their characteristic defensive posture—lifting the body erect, raising the first two pairs of legs high to reveal the banded underside pattern, and swaying side to side with hind legs cocked—is an excellent confirmation of identity. These spiders are called wandering spiders because they roam the jungle floor at night rather than building webs or residing in lairs, hiding during the day in termite mounds, under logs and rocks, and in banana plants or bromeliads. Some species, like *P. nigriventer*, seek dark, moist places near human dwellings. The genus includes some of the few spider species known to pose a threat to humans, due to a combination of venom toxicity, a tendency to bite, and proximity to human habitats.
- field
- Arachnology
- known_for
- Medically significant venom; defensive posture with frontal legs held high; common name 'Brazilian wandering spider'
Lore & Background
Phoneutria, commonly known as Brazilian wandering spiders or armed spiders, are a genus of ctenid spiders found primarily in northern South America, with one species extending into Central America. The largest members of this genus possess the longest body and greatest body weight among araneomorph spiders, with a leg span of 13 to 18 cm and a body length ranging from 17 to 48 mm. They are distinguished from related genera like *Ctenus* by dense scopulae (brushes of fine hairs) on the pedipalp tibiae and tarsi in both sexes. However, they are easily confused with non-medically significant ctenids, especially *Cupiennius*, as some *Phoneutria* species lack the red cheliceral hairs once thought diagnostic. Reliable identification features include a dark linear stripe or stripes on the dorsal palps, a single thin black line running anterior-posterior along the dorsal carapace, strong ventral markings on the legs with contrasting dark mid-segments and lighter joints, and a ventral abdomen pattern of several rows of black dots or an overall reddish color. A definitive behavioral indicator is their characteristic defensive posture: the body is lifted erect, the first two pairs of legs are raised high to reveal the conspicuous black-and-light banded pattern on their undersides, and the spider sways side to side with the hind legs cocked. The genus name, from Greek meaning "murderess," was established by Maximilian Perty in 1833.
Reader's Guide
Phoneutria holds significance as one of the few spider genera known to pose a genuine threat to humans. Danger arises not only from venom toxicity but also from the spider's capacity and tendency to bite, its wandering nature, and its proximity to human habitation. In densely populated areas, these spiders seek dark hiding places during the day, including houses, clothes, boots, and boxes, where they may bite if disturbed. Studies indicate that Phoneutria injects venom in about one-third of bites, with only a small quantity in one-third of those cases; only about 2.3% of bites (mainly in children) require antivenom. Fatalities, though rare, are usually attributed to respiratory arrest. The species P. nigriventer is responsible for most envenomation cases in Brazil because it is commonly found in highly populated areas of southeastern Brazil. The genus's legacy includes ongoing challenges in identification, as Phoneutria are easily confused with non-medically significant ctenids, and many historical reports of 'banana spiders' have been based on misidentifications.
Did You Know?
- The genus name Phoneutria comes from the Greek word for 'murderess'.
- Phoneutria can deliver a defensive 'dry bite' and inject venom in only about one-third of bites.
- The largest Phoneutria species have the longest body and greatest body weight among araneomorph spiders.
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