Spider scare provides view of foreign species

Wednesday, April 27, was a cool day, temperatures in the 30s with wet snow in the morning; not the kind of day that I would expect to hear about a tropical spider.

Wednesday, April 27, was a cool day, temperatures in the 30s with wet snow in the morning; not the kind of day that I would expect to hear about a tropical spider.

That changed when I received a phone call from a Duluth TV station telling me that Dan and Sheila Terry of Hayward had found a three-inch-long spider on a bunch of bananas.

They had purchased the bananas earlier that day in Superior, took them home and, after leaving the bag in the cool car for more than an hour, brought them into the house.

After subduing the spider, they notified the media about the incident. I was asked to identify the species. I was sent a photo of the damaged body, but from this picture, it was too hard to identify it positively. I needed to see the specimen.

We arranged a meeting, and on Thursday I was introduced to the tropical


spider -- well preserved in alcohol -- and its unintended owners. I needed

to magnify the specimen to get a good look at its face.

Spiders frequently are recognized by their faces. They typically have eight eyes, and the arrangement of these light-sensitive

organs can often reveal the family that they belong to.

I also wanted to see the chelicerae (the structures on the face that stick down below the eyes). A close look revealed the positions of the central or medial eyes. This spider definitely was a member of the wandering spider family (Ctenidae).

Being able to determine which species within this family was much harder to do. Setae (hair) on the chelicerae were red, a situation not usually seen with North American spiders.

References on how to identify tropical spiders are hard to get this far north, but using what I had on hand, I could determine it to be of the genus Phoneutria or Cupiennius. Both are often called wandering spiders. The name "wandering spider" comes from the fact that they don't make webs. Instead, using large eyes, they locate and actively hunt and pursue prey.

After determining it was a wandering spider, I was quickly asked about it being dangerous. That also was a difficult question. Virtually all spiders have venom. The poison is produced in glands in the head and goes from there to the fangs on the end of the chelicerae.


Venom is used to subdue prey (almost always insects) and is needed for the predator to survive. Many or most spiders are not strong enough or have large enough fangs to penetrate our skin. Almost all have venom too weak to hurt us. And most spiders are rather passive.

Was this tropical spider found in Superior dangerous? I'm not sure, but probably not.

Of the two suspected genera, Cupiennius is harmless despite its size and Phoneutria can be harmful. Toxicity of species varies, and those with strongest venom are further south in South America, less likely to be transported to North America.

All that can be said until an expert on tropical spiders sees the specimen is that it was a spider of potential danger; certainly not deadly as we may exaggerate it to be. This spider is an active hunter and so can be more aggressive than others. The danger of spider bites often is how strong or sensitive we may be.

If there was one on a bunch of bananas, there could be more; but the chances are very unlikely. This was a very unusual

incident. I suggest enjoying bananas as before. Let me know if another such spider is discovered.

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