Brown Recluse Spider

If you follow me on Twitter @JodyBugsMeUNL, you know a client brought me a brown recluse spider last week to confirm its identity. It was found in her garage inside a cooler that didn’t have a secure lid. It was the first live brown recluse that I’ve seen since joining Nebraska Extension in mid-March.

Brown recluse spider on finger

Body of the brown recluse spider was 3/8″ long and its legs were thin and long with no stripes, patterns or spines. Photo by Jody Green, Nebraska Extension in Lancaster County.

Because I am a spider person, I was pretty excited.

Because I respect my coworkers, this spider is now a preserved specimen in the lab. I didn’t release it in the building like I do with most spiders.

Often the spider samples I receive either in person or via photo/email come with the question: “Is this a brown recluse?” All samples until last Friday were negative. When I get a spider, I stick it under the microscope and look deep into its eyes. Usually spiders have eight eyes, but the brown recluse has six eyes arranged in pairs in a unique configuration. I’ve learned that the fiddle or violin shape shouldn’t be the prime physical identifier for this spider.

Close up of brown recluse spider cephalothorax and distinct eye arrangement.

Brown recluse spider eye pattern is very distinctive with 6 equal sized eyes arranged three pairs (dyads) in a semi-circle of the cephalothorax. Photo by Jody Green, Nebraska Extension in Lancaster County.

My favorite spider blogger, Catherine Scott, has an awesome post about how to tell if your spider is NOT a brown recluse. She is a Canadian arachnologist working on her Ph.D. at the university of Toronto, and it’s a process of elimination that is easy to follow (even without a microscope).

The brown recluse spider is one of the two medically important spiders in Nebraska, the second being a black widow spider. Both of these spiders have venom that can cause a negative reaction in humans. However, both of these spiders are considered non-aggressive and only bite in self defense. This occurs when they are trapped in clothing, bedding or shoes and someone accidentally steps, rolls or presses up against them.

Spiders do not require a blood meal to survive or lay eggs, unlike ticks, fleas, bed bugs, head lice, mosquitoes and other blood feeding arthropods. There is no economical benefit for them to bite humans, so they usually avoid using their venom. Spiders typically get blamed for the many mystery bites that show up on humans, especially when there are no witnesses to the bite or spider body (dead or alive) to identify. If you are concerned about spider bites and want to know how to avoid bites, Rick Vetter from UC Riverside is a great resource for all things related to brown recluse spider research.

Prey view of the brown recluse spider.

I call this the prey view of this male brown recluse spider. Photo by Jody Green, Nebraska Extension in Lancaster County.

When it comes to any biting pest, this is what I recommend:

  • If something bites you or you pick a bug off your body, keep it so it can be properly identified. That way, if you suffer any adverse reactions, your physician will know how what caused the reaction and the best course of treatment.
  • I cannot identify what bit you based on your bites/scabs/scars, and your physician won’t be able to either. Everyone reacts differently to bites – some have a delayed reaction, some are hypersensitive, and others do not react at all.
  • If you have a specimen for me to identify, please put it in a closed container or resealable bag (not on tape). If you do not have a physical specimen, but are suffering symptoms such as bites, rash, hives, itching, etc. Please see your doctor or dermatologist.

Keep calm and respect the critters,

Jody

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