[From my"Wild Ideas" syndicated newspaper column, January 2011]
Some people fear spiders in general — or are just sure that venomous Brown Recluse or Black Widow spiders are lurking in the dark corners of our houses waiting to pounce on us. The truth is that neither of these species is common in our houses and the arachnids that are more likely to be our housemates are innocuous ones commonly known as “daddy longlegs” because of their long, spindly legs.
The problem with the common name is that it is often used to refer to two different families of arachnids and even to an insect, the crane fly. Crane flies have wings and are insects, so that leaves us with the arachnids, cellar spiders and harvestmen.
A cellar spider
hanging around in a house
Photo by Sven Siegmund.
Cellar spiders, also known as “skull spiders” because of the markings on their bodies, are in the family Pholcidae of the spider order, Araneae. The most common of these species in Virginia homes is a European immigrant, Pholcus phalangioides.
Harvestmen, like cellar spiders, are arachnids but belong to the order Opiliones. Harvestmen are well represented on the planet, with more than 6,400 species having been discovered worldwide out of a total that probably exceeds 10,000, according to Wikipedia. Determining which kind of harvestman is in your house is a task best left up to entomologists, since the variations among species can be extremely subtle.
Harvestmen can be differentiated easily from spiders in that their multi-sectioned bodies appear to have only one oval segment instead of the two of spiders. The eyes differ as well: harvestmen have a single pair of eyes in the middle of their heads, oriented sideways, while Pholcidae have the eight eyes indicative of their order.
Cellar spiders, like harvestmen, have long legs, but they appear more spindly and frail and are often askew, which makes these ethereal spiders appear drunk or dying. Like cobweb spiders, their webs are messy.
Cellar spiders are effective predators, preying on mosquitoes, small moths, flies, gnats and other insects that often end up in our houses, as well as other spiders, even those much larger than themselves. They’re also fond of woodlice, a tiny terrestrial crustacean commonly called a “pill bug.” When food is scarce, cellar spiders can turn cannibalistic.
I recently saw a cellar spider with a Marmorated Stink Bug trapped in its web. The spider kept touching the bug with its back two legs. I couldn’t figure out if the spider was trying to determine what it had trapped, was intrigued by the scent of this other exotic invader, or was trying to figure out how to get through the bug’s hard carapace to the feast inside. In any case, by the next day the stink bug was gone — probably having escaped rather than ending up spider food. When disturbed, cellar spiders often shake their webs violently to ward off predators.
A harvestman (Opilio canestrinii), probably a female.
Photo by Pudding4brains.
Harvestmen do not spin silk, so don’t have webs. While they will occasionally eat small live insects, they mostly live off decomposing animal and vegetative matter.
Humans tend to have an uneasy relationship with spiders and their kin and can even be phobic about them. Maybe it’s because spiders are quick little predators that appear strange to us, are not exactly cuddly, can be aggressive and are in some cases quite venomous. We know so little about them, and there are so many of them, that we have a habit of spinning myths about them.
Take cellar spiders. Urban legend has it that they are the most venomous spiders on the planet, but that their jaws are too short or weak to bite through human skin. The television show “MythBusters” tested this myth by getting a spider to bite one of their onscreen reporters. The spider’s teeth did indeed manage to break through the skin, but the victim reported “nothing more than a very mild, short-lived burning sensation.” Researchers at the University of California, Riverside, back this up: “There is no reference to any pholcid spider biting a human and causing any detrimental reaction.” Some research shows that cellar spider venom is so weak it doesn’t even kill the tiny prey they normally use it on.
I used to freak out my friends when I was a little kid by letting wolf spiders crawl on my hands and bite me. I had the same sensation as that described in “MythBusters,” although the wolf spider’s bite was quite itchy after the fact. Harvestmen have no venom at all, but they do produce a harmless, albeit smelly, fluid when disturbed.
Harvestmen and cellar spiders are also decidedly nonaggressive. I’ve poked quite a few cellar spiders to see if they were alive, since they often look remarkably dead. Their only response was to shrink back a bit. And I’ve carried many a harvestman out of the house without them getting excited at all.
What isn’t a myth is that spider silk has antimicrobials in it, which makes sense, since spiders often catch prey that takes them a long time to consume, and antimicrobials preserve the nutrients. It is also hypoallergenic and so strong that the military is testing it for use in bulletproof vests.