Brown Widow

• GeneralIts egg sac is a spiky ball, unlike the black widow's.
• Drop for drop its venom is more potent than the black widow's, but it injects far less, so the bite usually amounts to local pain.
• Wherever it establishes itself it tends to displace the native black widows, taking over the same urban refuges.
• Its egg sac is unmistakable and gives it away before the spider itself does: a ball covered in points, like a spiky golf ball, quite unlike the smooth sacs of the other widows.
• The hourglass on its underside is orange or yellowish, not red as in the black widow.
• Its bite is far less serious than the black widow's, not because the venom is weaker but because the spider is smaller and injects much less. An African study of fifteen verified bites found none of the classic symptoms of latrodectism.
• It is thought to be native to southern Africa and is now found almost worldwide, carried with sea freight. It was detected in Miami in 1936 and reached southern California in the early 2000s.
• It competes with the black widow and is displacing it in several areas, which paradoxically reduces the risk of serious bites.

Habitat & environment

Walls, sheds, street furniture and gardens

Gestation / incubation

The eggs hatch in about 20 days

Litter / clutch size

From 120 to 150 eggs per sac, and up to 20 sacs over a lifetime

Sources consulted: Koch (1841); Vetter (2013), Universidad de California en Riverside; Mowery et al. (2022)