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One Of The Most Venomous Spiders In The US Is Dramatically Increasing Its Habitat Range Within The Country

One Of The Most Venomous Spiders In The US Is Dramatically Increasing Its Habitat Range Within The Country

Black widows and brown recluse spiders are the spiders that are most commonly associated with dangerous bites in the United States. Black widow spiders are considered by many experts to be the most venomous spiders that exist in the United States, but their venomous bites are rarely fatal to humans. In addition to black widows, an arguably creepier spider species that exists in the United States has sent numerous people to the emergency room due to their venomous bites, but few have heard of these non-native arachnids. The spiders in question are commonly known as yellow sac spiders, and two species have become established in the United States, one of which is commonly found in homes. Unfortunately, it is this species that is responsible for inflicting medically significant bites to humans.

Of the two sac spider species that exist in the US, one is native and commonly found in gardens and under leaf litter. This species is known as Cheiracanthium inclusum. The other species is not native to the US and experts disagree as to when and how it arrived in America. This species is known as Cheiracanthium mildei and it is commonly found in homes. Unlike its garden-dwelling counterpart, this latter species has been implicated in tissue necrosis that could possibly result from their bites. Because of this tissue necrosis, bites from the C. mildei spider species are often mistakenly assumed to be bites inflicted by brown recluse spiders, as brown recluse bites are known for causing tissue necrosis.

Both sac spider species are nocturnal, but it is the C. mildei species that is known for being active in homes at night where they skitter rapidly across ceilings and build resting sacs in the corner of walls and behind picture frames. This species is not aggressive toward humans or any other large-sized animals, but bites are relatively common considering their preferred indoor habitat. Bites from this species often occur when people accidentally lean up against their bodies. The C. midlei species has also become well distributed across the US as it is transported easily via shipments of agricultural products. This species was first introduced to Washington state either during the 1940s, or the 1970s.

Have you ever spotted a sac built by one of these spiders within an indoor area?