A European hammock spider, Linyphia triangularis, in her web in Troy. Photo by Dana Wilde

A few years ago, if you had looked up “European hammock spider” on the Global Biodiversity Information Facility website, you’d have seen a map with hundreds of yellow dots crawling all over Europe and into Russia, showing where the spider had been found and documented in its native range. Across the Atlantic, North America would have been completely empty.

Except for one lone dot on the coast of Maine.

Today, you’ll find a few more dots in Maine and the Northeast, including New Brunswick, and one far west in the vicinity of Vancouver. This is because the European hammock spider, also known as the dwarf weaver or Linyphia triangularis, sometime in the last 50 years or so found its way from Europe or east Asia to Down East Maine, and is slowly expanding its nonnative range.

Maine’s foremost arachnologist, Daniel Jennings, and Frank Graham Jr. tracked down the spider’s story after Graham found a sheetweb-weaving spider he could not identify near his home in Milbridge in 1991. (The two are the authors of the extensive study made for the U.S. Forest Service, “Spiders of Milbridge, Washington County, Maine.”) He showed his specimen to Jennings, and several years of arachnological sleuthing followed. They matched the spider to a previously unidentified specimen found in Brooksville in 1983, and eventually determined that “Linytri,” as they nicknamed it in their notebooks, was L. triangularis, a nonnative species of sheetweb weaver abundant in Great Britain and Europe but never before identified in North America. How it got to the coast of Maine is not known.

Linytri seems to have had a more or less immediate impact on the spider community in Down East. Studies in the 2000s showed that in areas where L. triangularis was living in high densities, other sheetweb weavers, such as the native bowl-and-doily spiders, filmy dome spiders and other hammock spiders, were declining or had been driven out altogether. Linytri was noticed evicting bowl-and-doily spiders from their webs and refashioning them to suit their own purposes.

Meanwhile, researchers working in Winter Harbor in 2002 found dewdrop spiders, which are cobweb weavers, inhabiting L. triangularis webs, and observed one of them eating a L. triangularis female in her own web. Dewdrop spiders are known kleptoparasites — stealing prey from other spiders. Now, apparently, they were eating the web owners themselves. Jennings had also found a juvenile dewdrop spider in a L. triangularis web in Pittston in 1999, suggesting it was already affecting spider ecology beyond the Down East coast.

The Maine Forest Service’s “Checklist of Maine Spiders,” compiled by Jennings, Charlene Donahue and the Forest Service and published in 2020, tags L. triangularis as an introduced, nonnative species that appears to be established; it’s been documented in every Maine county except Aroostook, and it would be surprising if it’s not living unnoticed there too. Linytri also fits the definition of an invasive species: not native to an area and causing disruption.

You might see one if you keep an eye out this summer. The main part of Linytri’s web looks more or less like a flat sheet, up to 6 or 8 inches in length and width, fashioned in brush or shrubs or even under a railing or on furniture on your back deck. The spider hangs upside down underneath the web and waits for bugs to get stuck. It then quickly cuts a hole in the web, pulls the bug through and then eats it or wraps it up for later. Often Linytri will return to repair the hole in the web.

Like all the spiders found in Maine and practically everywhere else, the European hammock spider is extremely unlikely to bite you. In fact, as far as anyone can tell, the only trouble it’s causing so far is in the spider community.

As far as your backyard is concerned, it’s just doing routine spider business, eating things that might otherwise try to eat you or your garden.

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 the second and fourth Thursdays each month.