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Top 10 things about brown recluse spiders

brown recluse spider, which can be found indoors and outside throughout the Midwest, including Kansas and Missouri. The photo shows its size in relation to a quarter. Image via Kansas State Research and Extension
Brown recluse spider. The photo shows its size in relation to a quarter. Image via Kansas State Research and Extension.

It’s brown recluse spider season. That’s the spider with the violin markings on its back – sometimes called the fiddleback spider, brown fiddler, or violin spider. Brown recluse spiders are rather shy and nonaggressive, but they have a powerful poison. Occasional bites happens because people and brown recluses often share the same living space. These spiders like dark corners and places inside the house, and also live under the furniture, boxes and books. From a research team at Kansas State University’s Department of Entomology, here are 10 things to know about these venomous spiders that like to live where we do:

1. Brown recluse spiders are found outdoors in the U.S. Midwest, as well as inside structures. They tend to thrive in the same environments that humans do.

2. Brown recluse spiders are venomous, but bites do not always result in large, necrotic lesions where surrounding tissue dies. Often, the bite goes unnoticed and only results in a pimple-like swelling. However, some people develop a necrotic wound (with blood and pus) which is slow to heal, with the potential for a secondary infection. If you know you’ve been bitten, catch the spider if safely possible, and show it to medical personnel for clear identification.

3. They readily feed on prey that is dead, so are attracted to recently killed insects. However, they can and will also attack live prey.

4. Brown recluses build small, irregular webs in out-of-the-way places but do not use these to capture prey. They tend to hide in the dark and move around at night searching for prey.

5. A brown recluse is tiny when it first emerges from the egg case and takes several molts to reach adulthood, six to 12 months. Remember, they are only active from March to October so this may take one to two years. Then they may live two to three years as adults. Females can produce two to five egg cases during this time (two or three is most common) and each may contain 20 to 50 spiderlings.

6. Sticky traps for spiders and other insects, available at most hardware and garden stores, work well to trap brown recluse spiders. They may not significantly reduce the numbers, but definitely help, and are a great way to detect and monitor the spider populations.

7. Brown recluse spiders are mostly only active from March through October, so trying to control them from October through March is generally not necessary or useful.

8. Insecticides labeled to control brown recluse spiders kill the spiders, but must be sprayed directly on them, or the spider needs to come into direct contact with the treated area while it is still damp. Otherwise, little control is achieved.

9. Brown recluse spiders are better controlled with insecticides on non-carpeted surfaces.

10. Preventative measures like sealing cracks in foundations and walls, clearing clutter in and around the home, moving woodpiles away from the house, placing sticky traps in low traffic areas and spraying pesticides can help eliminate brown recluse populations within the home.

Bottom line: Ten facts about brown recluse spiders.

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April 6, 2018

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