Polk County Conservation

Black Widow Spiders

  • My daughter found a black widow spider in an old tire in their yard. Are black widows indigenous to Iowa and how dangerous are they?

    Yes, black widow spiders are native to Iowa but they are not common. They can be found in logs and woodpiles around homes. Black widows are very shy and avoid light. They range in size from 1/8-3/8 inches long. The female black widow is entirely black with a red hourglass shape on the underside of her abdomen. Male black widows do not bite and are often eaten by the female after mating.

    All spiders are venomous. Their venom helps them kill or subdue their prey. Even though they are venomous, most spiders are harmless and won’t hurt humans. However, Iowans have to be cautious around brown recluse and black widow spiders. The venom from these two spiders can cause serious medical problems but is rarely fatal. Black widow venom can affect the nervous system causing nausea, muscle spasms and breathing difficulty in humans. Some people are slightly affected by the venom, but others may have a severe response. I wouldn’t be too alarmed. Just remember that spiders rarely bite humans and use caution when grabbing logs or reaching into wood piles.

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    Administration Office
    12130 NW 128th St
    Granger, IA 50109

    P: (515) 323-5300
    F: (515) 323-5354

    Monday – Friday, 8:00 a.m. – 4:30 p.m.

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