Spider Pest Authority
Identification, venom, and range data
Identify
Comparison

Western vs. Southern Black Widow

Functionally identical to medicine, ecologically separated by geography. Range is the cleanest separator.

Summary

Western black widows occupy the U.S. West; southerns occupy the Southeast and Gulf. Markings are nearly identical. Bite management is the same.

Diagnostic traits

Western vs. Southern Widow - side-by-side
TraitWestern Black WidowSouthern Black Widow
RangeCA, AZ, NM, NV, UT, CO, OR, WA, IDFL, GA, SC, NC, AL, MS, LA, TX, OK
HourglassComplete redComplete red
Venom potencyα-latrotoxin, similarα-latrotoxin, similar

The bottom line

At-a-glance comparison

Western Black WidowSouthern Black Widow
ScientificLatrodectus hesperusLatrodectus mactans
FamilyTheridiidaeTheridiidae
♀ body8–16 mm8–13 mm
Leg span25–40 mm25–38 mm
Range17 U.S. states23 U.S. states
MedicalMedically significantMedically significant