Black Widows
(Latrodectus mactans)

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Black Widow bites are painful and can include other symptoms such as fever, raised blood pressure, sweating and nausea, however, their bites are rarely fatal because there is an anti-venom available. To learn more about their bites, see treatments below.

Appearance
 
  • Females are about 1/2 inch in body length or 1 3/8 inches including legs

  • Males are about half the size of females

  • They have an almost spherical abdomen

  • They are black in color, but have a distinctive, red hourglass on the underside of their body

  • The hourglass doesn’t always meet in the middle so the shape can be slightly skewed

  • hey get their name from the belief that the females eat the males after mating

  • They are a venomous spider that is harmful to humans

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Behavior, Diet & Habits

Black Widows are nocturnal. You can typically find them in dark places such as garages, under potted plants, near fences, and other areas. They are solitary insects, except when mating. The females are normally shy but become aggressive when protecting their eggs.

The females spin irregular-shaped webs and hunt for prey at night. You can often find them hanging upside down from these webs so their hourglass warning is clearly visible. Black Widows are a venomous spider that is harmful to humans. The males’ venom sacks stop developing as they mature. Once they are mature they can no longer attack prey and their primary purpose becomes mating. Females are the primary concern for humans since their venom is a neurotoxin.

Reproduction

After mating, females deposit 6 – 21 silken egg sacs, each containing about 100 – 450 eggs. The sacks are white and quickly turn pale brown. The eggs hatch in 8 to 30 days and the new spiderlings will go through 4 to 9 instar stages in 50 to 150 days before becoming reproductive adults.

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Signs of an Infestation

Signs of infestation includes seeing a Black Widow, its irregular web, or receiving a bite.

Treatments

Black Widow Bites


Black widow bites don’t hurt immediately but the pain sets in quickly. There will be slight local swelling with two red spots where the fangs entered. Pain increases rapidly up to 3 hours and continues for up to 48 hours. Other symptoms include fever, raised blood pressure, sweating, and nausea. Seek medical help immediately and bring in the spider for identification purposes if possible. Since there is anti-venom available, bites are rarely fatal.

Property Treatment


To prevent further infestation, keep buildings in good repair, seal cracks and crevices correctly and remove clutter and debris from the premises to reduce harborage areas. We recommend removing webs and egg sacks buy vacuuming and sweeping and also recommend removing their food source. We recommend contacting your local pest control technician, who will inspect and identify the species, then apply the appropriate treatment.