Original illustration by PestControlBasics.com. Use anatomical labels above to confirm your identification.
Original illustration by PestControlBasics.com. Use anatomical labels above to confirm your identification.
Original illustration by PestControlBasics.com. Use anatomical labels above to confirm your identification.
🔍 Identification
Female: 8-15mm body; jet black (mature) with red-orange hourglass on underside of abdomen — the classic feature. Immature females may be brown with pattern. Male: much smaller; brown with pale stripes; rarely bites. Web: irregular, strong cobweb-type in low positions; thick, tangled structure that crackles when touched. Found in dark, undisturbed areas: wood piles, garages, under furniture, meter boxes, rock crevices.
🧬 Biology & Behavior
Western black widow range: western US and Canada. Southern black widow (L. mactans) overlaps in the Southwest. Females are sedentary — they stay in their web. Bite occurs when the spider is accidentally pressed against skin (putting on shoes, gloves, reaching into boxes). Venom: alpha-latrotoxin causes massive neurotransmitter release — the systemic syndrome is latrodectism.
⚠️ Damage & Health Risk
Latrodectism: severe muscle pain (abdomen, chest, back), muscle rigidity, nausea, sweating, hypertension. Symptoms peak 1-12 hours after bite. Death is rare in healthy adults but significant risk for children, elderly, and those with cardiovascular conditions.
🔧 DIY Treatment
Bifenthrin perimeter spray monthly during warm months. Sticky traps in garage and storage areas for monitoring. Reduce harborage (woodpiles, debris). Shake out shoes, gloves, and clothing stored in infested areas.
👷 When to Call a Pro
For heavy infestations in garages or storage areas, professional void treatment with residual spray and Delta Dust provides thorough coverage of harborage areas.