Q. My son is doing a science project on spiders. How common are black widow spiders around here?

A. Not very common, if they occur at all. We’re fortunate in the Northeast that we do not have to deal with poisonous spiders…usually. The only two seriously poisonous spiders in the U.S. are the black widow and the brown recluse spider. Some experts say that neither one occurs naturally in New Hampshire or Massachusetts. Although the black widow spider is more common in southern states, Massachusetts and New Hampshire are within the northernmost ranges of this spider. And, despite a lot of recurring national media and Internet attention about the brown recluse spider supposedly occurring everywhere in the U.S., the fact is that it occurs only in the south and central midwestern states. It does not occur naturally in the East or the western half of the U.S.

On rare occasions, black widow or brown recluse spiders may be accidentally transported to a new area in shipments or when people move from an area where these spiders are established. There is no evidence though that these occasional transports can develop into actual populations outside of their normal range.

So why then do we hear so much about people in our area being bitten by poisonous spiders? Almost always these are misdiagnoses, both on the part of the person bitten and by the medical community. Doctors are not pest control specialists and usually have little information on the actual distribution or occurrence of pests.

Another factor leading to misdiagnosis is the sensitivity of different people to spider bites. Even the reactions to a black widow bite vary widely from person to person. Some people may have an extreme reaction to the bite of a nonpoisonous spider (or other pest) that results in symptoms similar to a brown recluse or black widow bite. The belief that the bite was from a poisonous spider may be reinforced by the person’s physician. There are also many other medical conditions that can mimic a spider bite reaction. A normal reaction to the bite of a nonpoisonous spider for a nonsensitive person is local redness, irritation, and temporary pain that can be treated with a pain reliever and/or ice.

Keep in mind that there are other round, black, bulbous-shaped spiders that may look like the black widow but they do not have the red hourglass shape on their abdomen. And there are other spiders that, to the untrained eye, look like a brown recluse spider but without the distinctive fiddle shape on the back. For illustrations of both poisonous spiders, visit our Spider page in our Pest Library.