If there is any truth to the old saying that you are never more than three feet from a spider, it would be when you are in a garden in tune with nature. Even when you are not looking for them, spiders appear when you are weeding, harvesting, admiring that just-opened blossom, or when you reach into the garden mailbox for a spool of jute twine.
Many people, even some gardeners, have an undue fear of spiders. Of the 40,000 known spider species (3,400 in North America), only three are poisonous to humans: the black widow, brown recluse, and hobo spiders. Of these three, none are native to Maine while the black widow is found in southern New England. In fact, most garden spiders do not have fangs that are strong enough to pierce human skin or venom poisonous enough to affect humans.
The most numerous land predators on Earth, spiders are also among the most important predators in the garden. They are very effective in controlling insect herbivores (the plant eaters), even more so than birds or bats. Many species of spider survive the winter as adults that can be very effective in reducing herbivore populations at the beginning of the season, before other predators emerge.
Most spiders are generalist predators and so they do eat their share of beneficial insects, including pollinators, as well. Because of this generalist eating habit, spiders are rarely successful in controlling a large outbreak of a herbivore like the cucumber beetle.
Marjorie and I are accustomed to finding spiders in the garden, but every once in a while the unexpected spider will startle one of us. Such was the case this past weekend when Marjorie reached up to harvest a pair of ripe raspberries and almost grabbed a nursery web spider (Pisaurina mira) that was sprawled across both fruits, waiting for its prey to come close. It lingered there while we continued our garden work. Marjorie’s words as we closed the garden gate behind us were, “I really wanted those two raspberries!”
The nursery web spider was not interested in the raspberries except as a perch from which to hunt and capture prey. The female constructs a web only when her eggs, held within an egg sac, are ready to hatch. She hangs the egg sac within the web where the young spiders live under her protection until they are able to fend for themselves.
Also among the true spiders in Marjorie’s Garden are crab spiders, named for their sideways crab-like walk. I find them in open flowers, either lying in wait to capture their prey or consuming a captured butterfly, bee, or fly. Crab spiders are capable of changing their color to white, yellow, or pink over several days to make them better camouflaged within the blossom.
Spiders commonly known as orb web weavers spin elaborate webs in the garden. These spiral webs are architectural wonders designed to extend the spider’s sensory system and trap or slow down the prey with a minimal amount of energy expended in silk production.
I recently found a giant lichen orb weaver spider (Araneus bicentenarius) resting on a small sandstone caricature mounted on one of the garden fence posts, a human face with a very glum expression. At first glance I thought a lichen had started growing in one of Mr. Glum’s nostrils, for it looked exactly like the lichens found on old cemetery headstones or on tree trunks. Then I noticed its legs. Two days later it was still there, having moved only an inch or two to one of the eyelids. On the third day it had moved again, this time beneath an overarching brow in order to stay out of the rain. Rather than serving as camouflage, the lichen-like appearance of this spider made it more conspicuous. And where was the elaborate web?
Not true spiders, daddy-long-legs are equally important members of the garden food web. They eat aphids, caterpillars, beetles, mites, small slugs, and other plant-eating creatures. The daddy-long-legs in the photograph, Phalangium opilio, also called “harvestman”, was resting in the apex of a sunflower plant. In fact, this seems to be a favorite hangout for daddy-long-legs, perhaps because the surrounding whorl of young leaves hide the predator from leafhoppers and other likely prey.
In the garden, as in any functional ecosystem, everybody is somebody’s lunch. So what preys on spiders? Invertebrates such as centipedes and mantids, toads, wood frogs, skinks, nuthatches, chickadees, warblers, skunks, and shrews are some of the creatures known to eat spiders.
For the gardener in tune with nature there is little additional work needed to increase the number of garden spiders. Organic mulches such as grass clippings or shredded leaves provide protection as well as humidity that spiders must have. Apply these mulches early in the garden season when spiders are dispersing. Leave some areas of the garden untilled at the end of the gardening year to provide winter habitat in the form of plant stalks. And don’t be too tidy. Leaving a pot upturned or a tree stump to rot will provide microhabitats for spiders.
Whether you go about your gardening with little thought to spiders or take the time to search them out, rest assured that they are there, filling an important niche in the garden food web. Whenever you are in the garden, you are never more than three feet away from a beneficial spider.