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Identification of harmful and non-harmful spiders in central Ohio

It is my goal to identify the very few actual dangerous spiders in central Ohio, and to dispel all rumors concerning those that are not. I would like to start out by saying that any spider can be dangerous if an allergy is present, and that simply because you have a spider which you believe to dangerous does not make it so. Spiders should be treated with respect and care, and should not be handled without proper identification. I recently received a bite from a spider (the species of which is still unknown) and while it turned red and throbbed for several days, did not harm me. In central Ohio, only the Brown Recluse and the female Black Widow spider are dangerous. In your descriptions, please include detailed pictures and information about both venomous and nonvenomous spiders.

Spider venom allergy
Just a note about allergic reactions to spider venom- in order to have an allergic reaction a series of rare events need to happen. First you need to be bitten by a spider. Second, your immune system needs to decide that an allergic response is the best way to handle this particular type of venom in the future and make allergic antibodies (aka IgE) that can attach to that specific type of venom. Third, that same species of spider (or maybe another species within the same genus) needs to bite you again. Fourth, the allergic antibodies made in response to the previous dose of venom must bind to the newly injected venom, and trigger an inappropriate response from mast cells that fails to localize the venom.

Spider bites are fairly rare, but do happen. Most people require more than one exposure to a particular type of venom for their immune system to produce allergic antibodies against it, and it is very rare to have multiple bites from a single species of spider. Even then, the allergic reactions to arthropod bites and stings are usually appropriate and the reaction remains localized: an itchy red area at the site of the bite.

There are a handful of cases in which systemic allergic reactions to spider venom have been documented in a convincing way, but these reactions are so rare that they are probably not worth mentioning. Similarly, most recluse spider bites are similar to what you have described for your bite- a few days of a small, sore bump that gets better over time. Necrotic lesions almost never happen, and when they do, are concerning for something else going wrong with that person's immune system. Widow bites are usually not associated with problems, but the neurotoxins are capable of deranging the human nervous system, and this occasionally requires medical intervention.

Different people have different thresholds for what they consider to be “dangerous.” I usually reserve the term dangerous to refer to life-threatening reactions, but others think that several days of throbbing pain warrants the designation of dangerous. It is really a matter of opinion I suppose. Most spiders are capable of inflicting a painful bite similar to what you experienced. For that matter most predacious arthropods with piercing mouthparts are capable of giving a painful bite. I was once even traumatized by a grasshopper bite, although perhaps my pride was injured more than my skin. I think that fear is the most common consequence of spider bites, but ironically, spider bites even inspire fear in those that have not been bitten.

John, thank you for a reasoned and thoughtful response to what strikes me as a nonsensical request.


Answering questions
I enjoy sharing with other people the concepts that I find so fascinating. Finding out that it is the immune system that makes people feel sick is a bit like learning that Darth Vader is your father. "Good" and "bad" get all mixed up. Perhaps I am a bit overzealous in my writing on immune reactions to arthropods, but it entertains me and hopefully others will think it is interesting also. I really appreciate that BugGuide contributors share their knowledge with me on things that I know little about, and I certainly get far more excited about things such as tree crickets, goldenrod fauna, and spider anatomy than I would have if others had not shared their knowledge with me.

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