A nursery web spider mother watches over her spiderlings. Photo by Dana Wilde
I meant to curb my enthusiasm for spiders for a while, but we had an event in mid-July that must be shared. With those who want to hear about spiders, anyway.
Most mornings we go for a walk, and on the way out Bonnie checks the flower garden. All through June and July it was full of day lilies, purples, yellows and nascent sunflowers.
“Hey, look at this,” she said one morning, holding the leaves of a day lily. “It looks like an egg sac.”
Sure enough, under the leaves was a silk web holding what looked like hundreds of black, poppy-seed-size balls.
“Are they spider’s eggs?”
“Could be,” I said, but eggs are not my kind of esoteric arachnological specialty.
We went for our walk. When we got back an hour later, hundreds of tiny spiderlings had hatched — the technical term is “eclosed” — and were teeming excitedly inside their silk home.
Now given the shape and arrangement of the web, I had an idea of who they might be. They were nursery web spiders.
The mother was stretched out on the stem and orange petals just below the web. True to the species, Pisaurina mira, her relatively long body was marked with a rich brown stripe thick along her cephalothorax (head) and abdomen, flanked by a cream color along her sides. Nursery web spiders superficially resemble some wolf spiders by size, shape and markings, but their eight eyes are smaller and somewhat differently arranged on their faces.
One distinctive characteristic of nursery web spiders is their unusual mating routine in which the female and male dangle together on a thread, with the female wrapped loosely in silk. Afterward she constructs a silk cocoon in which she stores her eggs, carrying it under her body by holding it with her chelicerae, or jaws. When the eggs have matured, she finds a suitable site, such as underneath the leaf of a day lily, and builds a web where she stows the eggs and then stands guard over them. After the spiderlings hatch she keeps standing guard, which is what our nursery web mother was doing that morning.
There were two adjacent but different sacs of spiderlings for her to watch. Then one day I noticed she had consolidated the whole brood into one sac. There were probably, according to one study’s estimate, about 264 eggs, each about 1.15 millimeters in diameter. In our flower it looked like there were hundreds of little spiderlings. And no kidding, they were cute.
One morning while we were watching the ball of spiderlings, Bonnie spoke and they all jumped and scurried as if startled. After they settled back down, Bonnie waited a few moments then said, “Hello spiders!” and again they jumped and teemed as if startled. A few moments later, the same thing, though a little less frantic on the spiderlings’ part. I went to get the camera to see if we could get a video of spiderlings startled by a human voice.
When we got the camera going, Bonnie said “Boo!” and this time a few spiderlings hopped up and scuttered around, but the preponderance of them were now unfazed. The next time, only one or two jumped at the sound of her voice. When we tried it over the next few days, they paid no attention to us. We wondered if they actually registered the sound waves and learned there was no threat associated with them. Or had the mother been the one to register the sound, then signal through the silk for the kids to scatter, and after a few times, recognize, as the adult, that the sound was not a sign of a threat?
Five days after hatch day, I saw some tiny little nursery web spider exoskeletons caught up in the silk. Some had undergone their first molt, and the new juveniles had no doubt set off to fend for themselves. The mother was still standing guard. Two days later, eight days after hatch day, the nursery web was empty and the mom was nowhere to be seen.
I don’t think she was feeding the babies, just protecting them until they could go out on their own. Nursery web spiders are hunters, and only very rarely is one seen with a web built to snare food. Their cousins in the Pisauridae family are the fishing spiders, which are just about the largest spiders commonly seen in Maine. Fishing spiders live mainly near water (though we find wanderers up from our brook climbing on the house), while nursery web spiders usually live in brush on the edge of woods.
Most spiders do not care for their young, but it’s not exactly rare. Wolf spiderlings hatch out and then scamper up on their mother’s back, where they ride around for as much as two weeks before setting out on their own. Some jumping spiders, grass spiders and cobweb-weaving spiders care for their young. In an extreme case, mothers of some species of hackledmesh weavers guard the young spiders, then make the ultimate sacrifice — the kids eat them.
Anyway, we felt like our Pisaurina mira brood was the spidering highlight of the summer. And it was, for about two days, until we found another nursery web brood hidden away under another day lily. This one was about three or four days younger than the original family. These spiderlings also jumped when we spoke, then quickly got used to our voices, and a couple of days later, their little molts were dangling in the silk and they were off.
Off with, it turned out, at least four or five more broods whose webs were also hidden away in the day lilies. Little did we know in June that a veritable summer colony of nursery web spider families was setting up in the garden. What a world.
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.
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