Octicreepiness

We stayed with friends in South Louisiana for a while on our last expedition to collect field notes and images for classroom use and to go galumphing and visiting. Each night we would park our expensive rented car on their drive, swing open the wooden gate to their leafy, well-treed back yard and creep under the taut strands of a huge web strung by a palm-sized, yellow-and-black “banana” spider. The tremendous, spooky thing with a body as big as the first joint of your pinky and long, long spindly legs stretched out its intricate, golden web right over the walk every night. But it was a shy, or wise, character and would secret itself away from the human hub-bub during the day.

We grew up calling these fast, frighteningly large but apparently not too dangerous creatures banana spiders, probably because of their jazzy color scheme; maybe because folks thought they were shipped in on the speedy fruit boats which used to race over the Caribbean. When time ran out and we, our own selves, raced back to Japan to get back down to business, I was delighted to see the edges of light poles, bushes along the sidewalks, & the space between the uprights of road signs filled with what looked like a slightly down-sized cousin of our Louisiana friend.
The filament thin silk of their webs catches the morning and evening sun when I make my work commute a’foot. Not being a real “bugologist,” I have no idea if these are examples of the orb spinning nephila clavata, or the argiope, both descriptions seemed close on the world wide web. The clavata are common through China, Korea, and Japan and are alternatively called “mudang gumi” which in Korean means “fortune teller” for their utility in predicting certain future outcomes based on birth circumstances.

The fruit nick name, as I read on the electronic web, may be less useful than determining success of a proposed marriage, and is actually applied to two very different species of spiders. One, the argiope of North America, is pretty passive and benign, while the phoneutria of Central and South America, same by name only, can be deadly.

Much more aggressive, the South American banana spider, or phoneutria, has a large body--typically about 1.3" (3 cm). As a rule, this one makes its home in the rain forests. However, it is fairly adaptable and can also be found in cities. As a result, between 1970 and 1980 it was reportedly responsible for the hospitalization of some 7,000 people in southeastern Brazil.

If the Louisiana banana spider’s bite has been compared to a bee sting, the South American banana spider's injection is a neurotoxin similar to the venom produced by redback or black widow spiders. One specialist noted that “a phoneutria banana spider's bite will cause immediate pain, a cold sweat and irregular heartbeat.” The spiders here on Japan spin their webs all over the bushes, paths, and sidewalks. Unlike the critters in the US, they don’t seem to hide in the day. And, many Japanese could stroll under a head-high web before I’d walk face-full into the tiny nets which are surprisingly robust---the fibers are stronger than steel or Kevlar. Even without the venom, I suspect a face full of surprised spider would give me an “irregular heartbeat” for at least a little while. Some of these things are weirdly high, way up at the roof gables of two story houses. Then, it looks as if the huge creepy thing is just floating a few meters up in the air, levitating.
The regular argiope or so-called banana spider does have venom a lot like the toxin of the black widow, but it is apparently quite harmless to humans being a weaker, less potent concoction.

You probably know that males have it rough in the insect kingdom (and it’s not exactly a skate in the mammal world, either).

Anyway, according to a couple of Canadian biologists, some spiders have about the total nadir: they have sex then die. As a recent press release, devoid of any humor, noted, "the female doesn't have to do anything," said biology Prof. Daphne Fairbairn of the University of California Riverside. "He just dies spontaneously, he curls up his legs and he just hangs there."

Here in Japan the webs are plentiful. Its very easy to see the enormous female, colorful and prominent in the big sloping construction (spiders virtually always slope their webs in order to be able to sling themselves from below with the help of hooks at the tips of their long legs thus avoiding the stickiness of the silk material) with one or occasionally two or more much smaller males near by. As the news release explains, “the male orb-weaving spider, Argiope aurantia, is a quarter the length and about one-tenth the weight of the female. The male courts by waving his legs around, approaches the female and waits until she allows him to copulate. From our perspective, the copulation is unusual in that the male's sperm-carrying organ, which is called a pedipalp, is found in its legs.” This critter, observed on Australia, inserts his first pedipalp and releases some sperm. When he inserts the second one it swells and lodges in the orifice. At that point, as the report carried in the university press release puts it, “immediately the male becomes unresponsive, his heartbeat ceases and he dies.”

To get him out, the female actually has to break off the end of his pedipalp. Other males aren't strong enough to do it. What a way to go. Fairbairn and graduate student Matthias Foellmer of Concordia University in Montreal studied 115 matings to document what happens. "He's really acting as a whole body mating plug if you will, or a chastity belt," Fairbairn told CBC Radio's As It Happens. That’s pretty straight forward, after all, since you can see the benefit DNA wise. But over the week end we took a hike in the hill side near Tokyo and the foliage was alive with the vivid yellow and black spiders, with the reddish torso. Colorful plumage may help attract mates yet in this case the mate is about 5 body lengths away. He’s pretty much already attracted.

“Like the glitter and glare of Las Vegas beckoning tourists to the gambling tables, the orb-weaving spiny spider flashes its colorful back to lure unsuspecting quarry into its web. The discovery of this lethal use of color runs contrary to the long-held belief that in the animal kingdom color is used generally to attract mates rather than to entice prey,” says a Cornell University animal behavior researcher. Ah, that’s what I was wondering about. You’d really think most prey would more or less skedaddle at the sight of yellow and black.

"Attraction is all casinos are about. They lure you; they want to get you there. They lure people with bright lights, cheap plane tickets, inexpensive hotel rooms, great shows and great meals," says Mark E. Hauber of Cornell's Department of Neurobiology and Behavior. "The spiny spiders work the same way." Straight forward logic might suggest that “bright colors and contrasting patterns should be rare in predators that use traps, since conspicuous body color is scientifically counter-intuitive in stationary predators, says Hauber. Generally, he says, animals use "sit-and-wait" tactics in their concealed traps to capture prey, and colors and patterns only alert potential prey. Yet orb-weaving arachnids, such as the spiny spiders of Australia, are brightly colored and have contrasting patterns on their bodies. Hauber found that the more colorful their backs, the greater their chances of catching prey.

"It goes against what most scientists would have thought. Color is an attracting feature," says Hauber. "While color on animals like parrots allows them to blend into the colorful rain forest, other animals use color to attract mates. In this case, the color lures prey to the web. Perhaps the color itself may look like flowers to the insects that eventually become entrapped in the web," he says.
This scientist did not look at the same arachnids that I’ve been pausing to gander at, use as examples in my classes, and bother my students with questions about folk tales about. And it’s not safe to imagine that one animal defines behavior for another. But it is interesting that these spiders acted this way. Hauber observed spiny spiders (Gasteracantha fornicata ) in northeastern Australia. As a kind of test, he covered the yellow-black striped dorsal surface on the spiders' backs with ink from a black felt-tip pen. When he went over the data that slowly accumulated, he saw that the spiders with the black dorsal surface caught less prey than spiders with their normal colorful stripes. The implication was clear. A “treatment” was paired with a condition, and that condition was associated with the experimental circumstance. He did that “experiment” several times. (We can also say this is why “science” is not, as some pinheads imagine, a “religion.”) Anyway, the results gave him a pattern. Repeatedly he found that the blackened spiny spider always attracted and caught less prey.

"Perhaps the colors and patterns of their dorsal surface mimic the color of food -- such as flowers -- for visually oriented prey. It is also possible that the dorsal surface of the spiny spider is highly reflective in the ultraviolet part of the spectrum," he says. "Many flies, mosquitoes and gnats are attracted to bright light, and the kind of light rich in ultraviolet spectra, because these indicate the presence of field clearings adjacent to dense forests."

Hauber also learned that spiny spiders set their webs at an angle and that they sit on the underside of their webs with their backs to the ground. This suggests, says Hauber, that sun and nearby vegetation offer camouflage for the web. "Daytime web-building and hunting, along with the web placement and orientation, is consistent with behavior that attracts prey traveling from darker areas to lighter ones," says Hauber. Of course it’s well beyond my ken to speculate on the motivation of the many spiders we saw while hiking on that hillside an hour from one of the world’s biggest cities, rank upon rank of the webs seeming to have been sited to catch the sun more than to snag a meal. Is there any aesthetic notion to it? Or some great gearing to the chain of life?

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