Wild Ideas: Fall-breeding spiders sport Halloween colors  

Lately I’ve been enjoying watching fall-breeding orb-weaver spiders in Halloween colors spinning their webs on the outside of my house and in the woods surrounding it.

The orb-weaver family (Araneidae) constructs the iconic round webs most associated with spiders. Woven by the females, the webs hold cases of their eggs as trap prey. Like most of Virginia’s native arachnids, these spiders are neither aggressive nor dangerous to humans.

From spring through fall, orb weavers in the Micrathena genus of this family build webs across the wooded trails where I live from, especially the Spring Road, where I walk my dog at least once every day. These spiders are tiny, ranging from about a tenth inch to a half inch, with males half the size of females. These species appear to be pulling a nasty-looking trailer behind them, with three pairs of their legs up front and the last pair underneath their fantastically shaped abdomen, which has spikes (typically red with black tips) on it, especially at the rear.

Two micrathenas are common where I live: the arrow-shaped micrathena (M. sagittata) and spined micrathena (M. gracilis). The first has a yellow back shaped like an arrow; the other is black, with white blotches on its back, black-and-white stripes on its sides, and has spikes on its back as well as its rear. This fall, a new species in this genus has appeared, the white micrathena (M. mitrata). Its back is rounded at the front and has black markings on a white background.

Also new around here is a species that looks a bit like the arrow-shaped spider but is actually the arrowhead spider (Verrucosa arenata), in another genus. About the size of a micrathena, it appears to be carrying a yellow arrowhead — or wedge of lemon pie — on its back. Unlike other orb weavers, which face downward when waiting in the middle of their web for prey, the arrowhead waits facing upward.

If the prey that lands in an orb-weaver’s web is too big or not in her usual diet — such as the baby skinks I sometimes find there — the spider usually cuts it out. The nonnative brown marmorated stink bug also got this treatment when it first arrived here, but over time the orb weavers enthusiastically added it to their diet.

Another, drabber orb weaver, the barn spider (Neoscona crucifera), is usually the one I see the most around the outside of my house in the fall. This year one produced spiderlings inside a curled remnant of a plant that had stuck to the foundation.

The similar-looking but more spectacularly colored marbled orbweaver (Araneus marmoreus) is abundant this year. One of my favorite fall orb weavers, it, like the barn spider, is at least twice the size of the micrathenas, and the females of both species have fat, round bodies.

Female marbled orbweavers sport a mix of Halloween colors: bright orange underneath and on the upper parts of their legs, and, like most orb weavers, black and white bars on the lower parts. But it’s the back of this spider that is the real work of art: yellow-and-black patterns that vary, some like a randomly cut jigsaw puzzle, others with a symmetrical pattern of stripes, bars and spots. Sometimes they sport more- muted colors, and when the female is full of eggs, her abdomen can swell into a pumpkin shape and turn orange, which is how she got her other common name, pumpkin spider.

A female marbled orb weaver builds her web at dawn By Pam Owen

Last month a marbled orbweaver built her web across the Spring Road. Almost running into it on a dawn walk, I stopped just in time when I saw her busy wrapping up prey that had landed in it. Orb weavers usually wind just a few strands around their prey first and deliver enough venom to immobilize them before encasing them in silk for storage.

On my return trip, the spider was not in her web, but I was pretty sure where to find her. Although marbled orbweavers usually bring prey they’ve wrapped up to the middle of their webs, I’ve seen them construct lairs near a top anchor of their web that consist of a leaf rolled up into a snug funnel wrapped with a few strands of silk. The spider backs into it, sometimes bringing her meals with her. It also appears to serve as protection from predators and inclement weather. Sure enough, that’s where I found this orb weaver.

When I got back to the house, I found another marbled orbweaver constructing her web between the railings of my deck. When she finished, she went to the center, head facing down and with her front pairs of legs scrunched up, quietly waiting for prey, her feet feeling for vibrations in the web. Suddenly, she turned and bolted up to a fly that had landed in it.

Once the fly was encased in silk, the spider brought it to the middle of the web. In subsequent days, I found the spider had taken to lurking under the deck railing, which seemed a poor substitute for the leaf lair. She was usually devouring a stink bug, one of many that kept hitting the web on their way to my house in their search of winter quarters.

The stink bugs have all but disappeared now, and the marbled orbweaver on my deck seems not to have moved from her spot under the railing, even to mend her now-tattered web. In kneeling down to take a photo of her, I found her staring back at me. She looks about as fat as she can get, so either she’s just trying to digest the stink-bug feast or perhaps is getting ready to lay her eggs. (See a slideshow featuring this and the other spiders mentioned here below.)

It’s that time of year when Halloween decorations portray spiders as menacing villains. This year let’s keep in mind the value of spiders — and of bats, which are also cast as villains. Both help manage insect populations that can bring disease or destroy crops. Spiders are also fascinating to watch as they build their webs and otherwise go about their daily lives.

© 2018 Pam Owen

Pam Owen
About Pam Owen 338 Articles
Writer, editor, photographer, and passionate nature conservationist living in Rappahannock County, in the Blue Ridge Mountains of Virginia. Two favorite quotes: By E.O. Wilson, who coined the term "biodiversity," "Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction”; by Douglas Adams, “I love deadlines. I love the whooshing sound they make as they pass by.”