IDNR says the southern black widow builds its web throughout Illinois. The Illinois Poison Center says black widows are usually only found in southern Illinois. The two official sources differ.
IDNR: “The southern black widow builds its web near the ground in secluded places or indoors in sheds and barns throughout Illinois.” Source
IDNR: "builds its web near the ground in secluded places or indoors in sheds and barns throughout Illinois." … IDNR
What the sources say
Venom: “The venom of the female is very toxic to humans, but humans are rarely bitten because this spider is shy and not aggressive.” (IDNR)
Range: IDNR: "builds its web near the ground in secluded places or indoors in sheds and barns throughout Illinois." Illinois Poison Center: "Usually only found in southern Illinois". The two official sources differ.
Habitat: The black widow builds a web under objects in outbuildings, trash piles and other similar locations. (IDNR)
Official presence. 15 states where a state list or official source names it. Gray means no official record in our data, not that it is absent.
Native or listed
Nonnative or not established
No official record in our data
Observation records. Open-licence records on GBIF for the three US black widows (Latrodectus mactans, L. variolus and L. hesperus) in 44 states. Records are sightings people shared, not confirmation that a population lives there.
Chocolate brown and never has red on the belly; slightly smaller than a mature western black widow (about 3/8 in body length); egg sac looks like a cotton ball with indistinct margins. Caution: UC IPM says a black widow's hourglass can be almost imperceptible or, rarely, completely absent, so a lack of red alone does not rule out a black widow.
No red hourglass and not pure black; looks purplish-brown in bright light, and larger ones have a light T-shaped mark on the abdomen. Caution: a black widow's hourglass can rarely be almost or completely absent (UC IPM), so a lack of red alone does not rule out a black widow.
Usually a mottled mix of tan, brown and gray, with a lengthwise stripe and diagonal side stripes; colour varies from almost white to almost black, and very dark ones are flat black rather than shiny black. Mature females are smaller than mature female western black widows (about 3/8 in body length). The egg sac is covered in silk bumps, like a very large pollen grain; UC IPM calls the egg sac a much surer way to confirm a brown widow. Caution: brown widows also have a red hourglass on the underside (UF/IFAS), and a mature brown widow looks very similar to an immature western black widow (UC IPM).
Penn State Extension: the female common house spider is 5 to 6 mm long with a yellowish-brown carapace and a dirty-white to brown abdomen with gray chevrons; its legs are yellow with darker rings at the end of each segment.
