A huge fishing spider, Dolomedes tenebrosus, on the kitchen floor in Troy. Photo by Dana Wilde

This fall it came to my attention that a huge spider of mysterious species has been reported for quite some time on Islesboro. On the upper end of the island, to be exact. Reports describe the “up-island spider” being “as big as a windowpane,” up to 8 inches wide with its legs spread. It has red eyes, and has been heard running across floors, or maybe ceilings, in the night.

To be clear, I have not been to Islesboro in more than 40 years, and at that time did not see (or hear of) this legendary spider. Many sightings seem to occur in the vicinity of an old church on the upper end of the island, leading to the idea that the spider arrived long ago from the mainland in a coffin. So it’s also known as the “hearse house spider.”

Now, the World Spider Catalog as of this month lists 49,720 officially identified species of spiders. Arachnologists are confident that many more undiscovered species share planet Earth with us — from 75,000 to possibly as many as 190,000 spider species. At least 677 species are at home in Maine, as listed in the Checklist of Maine Spiders published last year by the Maine Forest Service. There are no doubt more. (I found one this summer, the American green crab spider (Misumessus oblongus) which is thought to be present here but had never been tagged.) So strictly speaking, it is not impossible that a unique spider species inhabits a limited area on one of Penobscot Bay’s larger islands.

It does, however, seem extremely unlikely. So I conducted an unscientific internet research mission to see if I could figure out what the up-island spider is.

Some reports describe huge spiders with tiny spiders riding on their backs. This sounds weird! But it’s not, really. In fact, it’s perfectly normal: Wolf spider mothers carry their kids around on their backs for a couple of weeks after the eggs hatch. Also, some wolf spider species can be startlingly large (up to a half-inch in body length); their eyes are constructed like human eyes and can shine red (or green); and they’re the most abundant family of spiders found in Maine, including on islands.
Sure enough, among the photos posted online of up-island spiders, some of them are plainly wolf spiders.

There are some startlingly large orb weaver spiders in Maine, too. We found an Araneus saevus female stumbling across the driveway this fall, probably having fallen out of a tree after laying her eggs; she was a good inch from head to toe. And the similar looking barn spider, aka Araneus cavaticus, the model for E.B. White’s Charlotte, can be even bigger. Startlingly large orb weavers almost certainly make their home on Islesboro.

Probably the overall largest spider you’re likely to see in Maine is the fishing spider, also known as a wharf, dock, or raft spider. It lives principally near water, as the name suggests, but also wanders into houses. Female Dolomedes tenebrosus, a fishing spider commonly seen in Maine, can be an inch or more in body length. Add eight long, banded legs, and you have a spider big enough to startle you into thinking it’s way bigger than it actually is. I opened my eyes one night to see, on the wall a few inches from my face, a fishing spider so huge I wondered if she was after the cat. (Just joking. She only seemed that big for a few seconds.)

This photo from a Wikipedia page shows the “up-island spider” of Islesboro, Maine. It is almost certainly a species of the large fishing spiders (Dolomedes spp.) commonly seen in Maine. Photo from Wikipedia

So not surprisingly, many of the up-island spider photos posted online are of fishing spiders.

I think it’s extremely unlikely that a unique spider species lives only on one limited area of Islesboro, and much more likely that fishing spiders, sometimes wolf spiders — maybe an orb weaver or even a nursery web spider — are seen that are so startlingly large they seem bigger than they really are; get even bigger and more detailed in the story of the sighting; and turn humongous when the story gets woven in with the other tales that make up the legend of the up-island spider.

In Edgar Allan Poe’s story “The Sphinx,” a man is gazing out a window when he sees movement on the hill outside. To his horror, an enormous devil-faced monster creeps into view, and he begins to panic. His friend calms him down by showing him there is no creature on the hill at all. Climbing a strand of spider silk in the window is a tiny sphinx moth so close to his face that he thought it was a giant.

I heard a rumor this summer about an outbreak of enormous spiders in the Lewiston area. I don’t know for sure, but I have a feeling this story has origins similar to those of the up-island spider and Poe’s Sphinx. I’m sure people were startled by large spiders they’d never noticed before. But I’m betting the spiders were there all along, just unnoticed until everybody started pointing them out.

Dana Wilde lives in Troy. You can contact him at naturalist1@dwildepress.net. His book “A Backyard Book of Spiders in Maine” is available from North Country Press. Backyard Naturalist appears on the second and fourth Thursdays each month.