Black Widow Spiders #709778 - Ask Extension

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Black Widow Spiders #709778

Asked August 05, 2020, 12:33 PM EDT

Hello, We have lived in Maryland for nearly 7 years. We have never run into Black Widow Spiders near the house and in the past month we have become acquainted with 3 and 1 with her egg sack. Is this "mating season" or a prolific year for them? Additionally, what measures can we take to keep them away from the house? We don't want to kill them, but we have little ones and an elder to keep safe.

Calvert County Maryland

Expert Response

Both Northern and Southern Black Widow species are found around Maryland. There is no data on their population fluctuations in the state, but if prey insects are having a particularly good year (or did recently), their predators (like spiders) will increase as well. In time, spider mortality will increase as their own predators have their population boom. The cycle continues and species numbers dip and rise over the years, which is often tied to weather. Since you have three adults in the area, it's possible an egg sac made its way into the yard earlier this year by hitching a ride on objects like firewood, cinder blocks, wooden boards, plant pots, or other outdoor objects with cracks and crevices. Black Widow spiders start reaching adulthood this time of year, so males will be in search of females. (This one evidently had one find her already.)

Widows tend to be very reluctant to bite, even when molested - they often drop, tuck their legs in, and/or play dead - though bothering one of course should be avoided, especially by children. Someone could attempt to capture the spiders one at a time (with gardening gloves on) in a clear container to relocate them (and the egg sac) to wild vegetation outside of the yard. These spiders can live up to about three years, so they won't necessarily perish over winter.

You should not need to worry about them entering the house unless they are accidentally brought inside on objects stored outside. They are very clumsy walkers when not in a web, and only tend to disperse when young. (Males will wander to find mates, but their venom is far less potent.) There is no easy way to keep them out of outdoor toys or objects if those objects have tight spaces where the spiders will prefer to build their webs and hide from predators. If absolutely necessary, crushing the spiders and eggs or spraying them with a labeled pesticide (for spiders) should work. Otherwise, as with any other arthropod potentially invading a home, simply make sure all cracks, holes, or gaps are sealed and that window screens are intact.

https://extension.umd.edu/hgic/topics/spiders-maryland

Miri

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