— BugsInTheNews is a VIEWER-PARTICIPANT WEBSITE. This article by Jerry Cates, Kevin (Junction, TX), and Dave R. (McKinney Falls State Park, TX), first published on 2 February 2011, was revised last on 7 July 2012. © Bugsinthenews Vol. 12:02(02)
The order Opiliones, in the class Arachnida, was first described in 1833 by the Swedish zoologist Carl Jacob Sundevall (1801-1875). The English naturalist and physician, Martin Lister (1638-1712), was honored by Sundervall’s choice of this name, as Lister had used it in earlier descriptions of three species from England. The epithet is derived from the Latin opilionis, which means “a shepherd,” and likely refers to the fact that certain species of these spiders form conspicuous aggregations, their congregations appearing as huge herds of animals.
The source of the common name, harvestmen, is — according to the American entomologist and arachnologist John Henry C0mstock, writing in “The Spider Book” (1912) — probably suggested by the fact that they are most often seen at harvest time. That name is preferred to daddy longlegs, says Comstock, as the latter is also applied to crane flies. In some areas the harvestmen were known as grandfather graybeards. In England they were apt to be called harvest spiders and shepherd spiders; in France, they were called faucheurs, or hay-makers.
The order is presently subdivided into four suborders, in which some 6,476 species are now recognized worldwide. By far the largest suborder is Grassatores, which contains 3,559 species, nearly 55% of the total. It is believed that the number of recognized species in the order Opiliones will eventually rise to at least 10,000.
Though often mistaken for spiders, harvestmen differ from spiders in several anatomical characteristics. Their bodies are not divided into two separate sections the way spiders are, but — although they are positionally arranged according to a separately functional head, thorax, and abdomen — the body parts are broadly fused to form what appears visually as a singular, oval, corpus.
They have no venom or silk glands, and their tiny chelicerae, though grossly similar to spider fangs, are too small and fragile to break human skin. Thus the myth that these are the most venomous creatures on earth has no basis whatever.
Many of the Opiliones are cave dwellers, and some have lost their eyes altogether. All sighted Opiliones have but two eyes, perched upon the middle of the head, and oriented so as to survey the lateral environment, rather than looking forward or backwardward. This is not a significant impediment, as the animal’s spindly legs enable it to reorient the body with some agility in order to view a panorama of environment at will. Respiration is via tracheae alone, as the book lungs common to most species of spiders are absent. Copulation, which in spiders is indirect (the male spider discharges sperm into a specially constructed sperm web, then charges the pedipalps from the contents of the sperm web prior to mating), is direct in the Opiliones. The male has a penis, and the female gonopore is on the ventral cephalothorax.
My good friend, Abel Pérez-González, an opilionologist at the Federal University of Rio de Janiero, Brazil, is one of the world’s leading authorities on the order Opiliones. I hope one day to cajole him and his mentor and fellow opiolonogist, Adriano B. Kury, into contributing some terse and pithy comments here, as well as some of their photographs and drawings of Opiliones anatomy…
ENCOUNTER 04252010 KEVIN, JUNCTION TX:
When Kevin sent me this photo, he was curious to know what kind of spider it was, and if it might possibly be dangerous.
My reply was that it was — rather than a spider — a harvestman, and inasmuch as not one of the organisms in the order Opiliones has venom glands, they are harmless.
Unless, of course, the peculiar fragrance of the defensive discharge from their prosomal exocrine glands, which open to the surface as ozopores (Greek οζω, “ozo”, smell) assaults your olfactory senses.
I know, this page is about a harvestman found in Texas, but for a moment I’ll digress a bit to say something about the harvestmen of rural Missouri.
The odor produced by the ones I remember finding as a child in the Ozarks (each species produces a unique mixture of chemicals) is sickly sweet; perhaps the best one can say is that it’s anything but attractive, though whether it is fiercely offensive depends on the sniffer.
I cannot get a whiff of that odor without thinking of my paternal grandmother’s storage barn, in rural southwest Missouri.
She stored old furniture and clothing there, and over time it had become a haven for huge numbers of harvestmen.
In the late 1940′s, when just a kid, I would sometimes sneak into the barn, when nobody was looking, to hide from my older brother while we played our childhood games. My hide and seek meanderings disturbed masses of these arachnids to the point that they spewed enough musk to make me choke.
But not enough to make me ill. Actually, though the ozopore emissions of the Opiliones are commonly believed to be primarily defensive in nature, Schaider & Raspotnig (J. Arach. 37:78-83, 2009), as well as a number of other investigators, have shown that, at least in some Opiliones, a number of other purposes may be involved. These include their utility as antibiotics, territory markers, and as alarm and aggregation pheromones.
Kevin’s specimen, inasmuch as it was photographed on one side, without providing much in the way of detail, cannot be identified to a specific suborder, much less to species, at least by me. However, it does show enough features to definitely place it in the Opiliones order.
ENCOUNTER 08222010 DAVE R., MCKINNEY FALLS STATE PARK, TX:
My girlfriend and I are both new to Texas, and both of us love nature, so we’ve had some interesting encounters with our 8-legged Texas friends.
The picture is of some daddy longlegs, and yes, I know they aren’t spiders but I also know they aren’t moss.
That’s what I mistook them for when I spied them resting under an overhanging rock, en masse.
Boy was I surprised to see them start walking out of the pile when I reached out and touched the “moss”…
(Dave’s surname has been shortened to protect his privacy)
Lots of us have had Dave’s experience. And though he didn’t say so, he likely was rather fearful of the critters that suddenly started moving about when his hand intruded into their space.
Though we know they are harmless, the very idea of thrusting one’s hand into the mass of these animals is repulsive. One of these days, though I’m going to have to do that… just because.
Notice that these harvestmen are truly long legged. Their legs have narrow pale bands at the distal femur, and broader, pale white bands at the distal tibia of each leg.
These adaptations make the legs highly visible, especially when the animals move about when disturbed, and serve to warn potential predators that the mass of arachnids is composed of live animals, not moss or some other plant or fungi.
It seems likely that these organisms aggregate as they do for purposes of protection against predation. Some species, when disturbed, are capable of rhythmically extending and retracting their legs, en mass, giving the impressive, awe-inspiring illusion that the wall or ceiling they are congregated on is moving.
Dave, a mathematics professor and paleontologist, also contributed a photo he took of a field wolf spider. Because of his interest in fossils, I hope to get him to accompany me on a hike to inspect and take new photographs of some of the dinosaur footprints that have been uncovered in central Texas.
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