'The Leaping Dancer'
by Bill Amos, US

Images by Dave Walker

If the man in the film who explained, "Honey, I shrunk the kids," turned his attention to you, and you ended up one centimeter tall (about a third of an inch), then found yourself on the lawn, you would have your work cut out. You sit underneath a clover leaf trying to comprehend the strange world around you. The soil heaves as squelching sounds rise to the surface; beneath you an earthworm is shoving its noisy way through the moist earth. Not far away, grass blades bend and snap back and the earth trembles as an immature grasshopper— size of a young heifer in your present scale—, stopping to rub its eyes clear of pollen dust with its clawed front legs. Caution prevails and you remain motionless, hunched under your three-bladed leafy umbrella.

The grass-jungle world grows silent as the insect rests. From your hiding place, you inspect the extraordinary brown-and-green creature with its multiple mouth parts, its multi-faceted eyes, accordion-pleated abdomen, strong jointed legs and budding wing pads. Minutes later you hear an indistinct sound beyond your field a view, a slight tapping, then all is still again. Time and again the faint pattern repeats itself, gradually coming closer.

The relaxed grasshopper basks in the sunlight and the warmth of the soil, flicking its antennae, mostly to pick up subtle odors, for these long slender shafts contain organs of scent. The unidentified rustling becomes more pronounced until on the other side of a small clearing you see a dark, hairy creature— you the size of a small bear—, like you, is partly hidden behind a blade of grass. It creeps forward and bends around the plant stalk to peer ahead. Seeing the insect, it stops and remains still. Sunlight reflects from iridescent blue-green appendages folded down along the front of its head, each bearing at its tip a curved, needlelike fang. You find yourself looking into a pair of huge dome-shaped eyes, noticing another smaller pair directed outward on the sides of the head, and a straight, even row of four lesser eyes beneath the main pair. The legs of the animal— are eight of them— brushy with coarse bristles and the dark, partially striped body is thickly furred, although you know it is not fur at all.

Because you are well-read, you realize you are looking at a jumping spider, a predator that hunts by stealth rather than spinning a web. You know too that its immense staring eyes, unlike those of other spiders and all insects, are capable of forming precise images that convey meaning to a well-developed brain. You freeze, hardly daring to breathe.

The young grasshopper, slightly larger than the jumping spider, is oblivious to danger and continues to wave its antennae lazily above its head. The spider remains about a dozen grasshopper-lengths away. Catlike, it hunches down, its rear legs folding underneath its abdomen as it adjusts itself, moving slightly from side to side. Its large eyes, serving now as rangefinders, gather information about distance to the insect. Its third pair of legs provide stability to the body while the first two pairs extend slowly out in front. All is quiet for a moment. Then, faster than your eye can follow, the spider launches itself forward with its rear legs in a single prodigious leap, trailing behind a thin strand of silk anchored to the ground. The furry body lands solidly on the grasshopper that is instantly aroused, but its own more powerful rear legs are not in a folded position to spring away and it goes nowhere. The sturdy insect is immediately frozen into immobility as the spider enfolds it with powerful legs and injects a paralyzing venom from the twin fangs. The victim's movement ceases.

Jumping spider Soon the toxin liquefies the insect's tissues and the spider, possessing no real mouth parts, begins feeding on the fluid contents from the dead grasshopper, its large stomach pumping rhythmically, forcing nourishment into empty chambers that extend into the bases of its eight legs. With more food than it can utilize, the predator remains in place for many minutes, feeding to capacity, while you creep away from the scene. Your movement now holds no interest to the feasting spider. Whether it was a dream, or the spell cast by the man who shrank you and his kids was only temporary, you find yourself back in your normal world, towering over the miniature jungle under your feet.

A jumping spider is one of the most fascinating of all spiders, although there isn't an arachnid anywhere that is not a complex and wondrous creature— the aversion most humans feel for these eight-legged predators. We marvel at the courtship displays of birds and mammals, fishes and lizards. But spiders?

Jumping spider Each species of jumping spider has a language all its own to communicate with others of its kind. With over 4,000 species of jumping spiders world-wide, such distinctions are necessary to avoid living in a veritable Tower of Babel, especially when a male invites a female to bear his young. He also "speaks" to other males, warning them away with body-language intended to intimidate, as he edges sideways, legs held in a formalized position, abdomen bent almost parallel to his adversary, displaying his size and readiness to fight. As a suitor, a jumping spider's message is conveyed mostly by his front legs, sometimes adding the next pair for emphasis, although acrobatic dances also enter into his frenetic invitation. He rears back on his hind legs, swaying and lunging and rocking sideways, waving his enlarged front legs held straight out, semaphoring and zigzagging, up and down, dancing back and forth in ritualized fashion. The female answers in her own manner with her more slender front legs as the dialog continues.

One species cannot understand the ceremonialized dialect of another, so mistaken matings don't occur. Even stationary, there is no confusion of identity. When held aloft, the under sides of a jumping spider's front legs may be colored or iridescent to accentuate the message, a living billboard ensuring positive identification. Depending upon the species, the face of an ornate tropical jumping spider may be metallic green or iridescent blue, decorated with brilliant red or orange scales and tufts of hair, and its short leg-like palps are clothed with snow-white hair. (More conservative northerly jumpers are not quite so garish.) The extravagantly decorated male prances in front of the female, who watches his posturing intently. If she is receptive and finds the invitation irresistible, she still may play hard to get, darting off or engaging in a mock attack, eventually lowering and bending her abdomen toward him. They circle one another in an elegant minuet, perhaps embracing before the mating process is consummated. Another male of the same species, his huge eyes picking up every signal of the elaborate courtship, decides to avoid conflict and moves away, although if he is somehow more formidable, he may challenge and perhaps drive the first male away.

Because of jumping spiders' excellent eyesight, such exchanges by each participant can be carried on over considerable distances, even a foot or more. These spiders are catlike and use every surface feature to hide behind, stalking their prey and one another as rivals or potential mates. Not being restricted to one spot, their territories are extensive and they move with ease up tree trunks, stone walls and through meadows. Being out on a limb is no problem for a jumping spider. It looks for a likely place to land, then leaps into space, thrust forward by its hind legs that now extend rearward. Trailing behind is a strand of silk anchored to the branch and drawn by the spider's momentum from the spinneret glands at the tip of its abdomen, a safety line in case distance has been misjudged, or if for some reason the spider needs to return to its original perch. Should this occur, the animal catches the silken strand with comblike claws on the tip of each leg, whirls about and quickly skims up to the branch it has just left. Otherwise, after a safe descent, it severs the lifeline. Some spiders may consume it, for the protein in spider silk is not to be wasted.

I have watched jumping spiders at work in many parts of the world and find them astonishing creatures— then, every species of animal is wondrous when left to its own devices and seen in its natural surroundings. It is just that catlike jumping spiders, with their sometimes brilliant colors, their agility and sufficient intelligence to meet their needs, are enormously appealing— only one of my children doesn't say, "Hey, Mom, I just shrunk Dad!"

1993 William H. Amos

Bill Amos is a retired zoologist, ecologist, author, and microscopist who lives in northern rural New England.

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