Life on a Thread

By Matt Seek | October 1, 2024
From Missouri Conservationist: October 2024
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Bold Jumping Spider
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Life on a Thread
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The attack, when it comes, is swift, decisive, and lethal

A whisper on the grass betrays the gathering of feet. A bold pounce bridges the gap between hunter and quarry. Predator and prey tumble over each other, one desperate to escape, the other to restrain. The violence lasts only a second, perhaps two. And then the prey, once so agile and alive, lies still and dead.

The ambush, familiar to anyone who’s watched nature documentaries, doesn’t occur on an African savanna and isn’t perpetrated by a big cat. Instead, the struggle plays out on a single blade of big bluestem, the prey is a flower fly, and the predator is a tiny black jumping spider, no bigger than a pencil eraser.

One Big Family

Imagine you could stuff one of each kind of spider on Earth into a bag. For every eight times you reached inside, you’d likely pull out at least one jumping spider. According to the World Spider Catalog, of the planet’s nearly 52,000 species of web-slingers, more than 6,600 are members of the jumping spider family, Salticidae. The family is so large, its species tally outnumbers the combined total of all mammalian species.

Salticidae isn’t just the largest spider family, it’s also the most cosmopolitan. Wherever in the world you might go, if you look closely enough, you’ll probably find a jumping spider looking back at you. Odds are, there’s probably one watching you right now.

Jumping spiders are found on every continent except Antarctica, and they inhabit nearly every habitat, from sunbaked deserts to soppy rainforests. In 1924, Richard Hingston, a medic on the British Mount Everest expedition, observed tiny, coffee-brown spiders living among rocks 22,000 feet above sea level. Decades later, his samples were identified as Himalayan jumping spiders, thought to be the world’s highest-living spider.

Salticids range in size from tiny jumpers in the genus Neon, most of which are no bigger than a flake of coarsely cracked black pepper, to the tropical hunters of the genus Hyllus, some of which may grow up to an inch long. A few jumpers are so flamboyantly colored they’ve been given the moniker “peacock spiders.” Others are so perfectly camouflaged you could stare right at one and fail to see it. Some jumpers mimic herbivorous leaf beetles and use their disguises to dupe unsuspecting prey. Other jumpers mimic biting ants or stinging wasps in an attempt to make would-be predators think twice about making them a snack.

Despite their vast numbers and variety, one trait makes it easy to differentiate a jumping spider from any other kind of arachnid: its eyes.

Mighty Sight-y

Like most spiders, jumpers have eight eyes. But unlike many of their cousins, jumpers see exceptionally well. And it’s the unmistakable arrangement and structure of their eyes that sets salticids apart from other spider families.

In the middle of what you might call a jumper’s forehead rest two oversized, alien-looking eyes. On either side of those are two smaller front-facing peepers. The other four eyes are arrayed like running lights — two on the left, two on the right — on the spider’s cephalothorax (the front half of the body to which the legs are attached). The middle pair of these “lateral eyes” is indistinct and often hard for amateur spider watchers to spot.

The large principal eyes are fixed to the spider’s head like portholes on a ship. A telescopelike tube extends backward from each lens to the spider’s retinas. To look left, right, up, or down, the spider moves the “eyepieces” of the telescopes (the retinas), not the portholes. In semi-transparent species, you can watch from overhead and see the tubes shifting around inside the spider’s head.

The large eyes empower jumpers with the highest visual resolution of any animal less than 20 millimeters long. In fact, a jumping spider’s vision is comparable to much larger animals like pigeons or dogs. But this stunning clarity comes at a cost.

Jumpers, because they essentially see the world through twin telescopes, have an incredibly narrow field of sharp vision. It’s like using the beam of a flashlight to explore in the dark — you have no idea what’s going on outside that tight circle of light. And that’s where the other six eyes come into play.

The lateral eyes aren’t nearly as powerful. The world, through their lenses, is blurry and gray. But what they do detect well — in a nearly 360-degree field of vision — is motion. Being able to spot movement approaching from any direction is a huge advantage for a tiny animal that is both predator and prey. The lateral eyes, then, have an important job: They tell the principal eyes where to look. And often what they decide to look at is their next meal.

Leap of Fangs

Jumping spiders don’t weave webs. Instead, they use their keen vision to find prey and then sneak as close to it as they can without being detected. Once they’re within range, a jumper gathers its legs and — sproing! — pounces, catlike, on top of its victim.

Some species — including Colonus puerperus, a colorful jumper common in grassy areas throughout Missouri — can leap horizontally up to 40 body lengths. Jumps from a slightly elevated position can stretch up to 50 body lengths. To achieve the same feat, a 6-foot-tall person would need to broad-jump half the length of a football field.

With such an impressive jumping ability, you’d be forgiven to think that salticids sport Olympian-sized leg muscles. But they don’t. Their long-range leaps result from blood pressure, not muscles.

Think of a jumping spider’s body as an eight-legged water balloon. Squeeze one part of the balloon, and the other parts expand. By constricting muscles in its cephalothorax, a jumper forces hemolymph (the spider equivalent of blood) quickly into its last pair of legs. In a millisecond, the legs violently extend, and the spider rockets off into space.

Before leaping, jumping spiders secure a strand of silk to their launch site. They use the silk as a dragline to control the length of their jump. And if they overshoot or fall, they can ascend the dragline, like a mountaineer crawling out of a crevasse.

Dangerous Dating

Pouncing on prey and being snack-sized yourself makes a jumping spider’s life inherently risky. Yet nothing, perhaps, is riskier than meeting another jumping spider. Protein is protein, and jumpers rarely pass up a meal, even if it happens to be a fellow spider. Female jumpers, on average, tend to be bigger than males. So, when a lovestruck male meets a female, one of two outcomes will occur: He’ll either find a mate or have the worst (and last) day of his life.

To tip the odds toward the former, male jumpers perform elaborate dances. From a safe distance, a courting male lifts his front legs and waves them rhythmically. Like male songbirds, many jumpers are adorned with bright colors, and the raised legs permit a better view of the eye-catching hues on his head and jaws. Once he’s caught the female’s attention, he might shuffle from side to side or bend his abdomen jauntily to the left or right.

To express his desire (not to be eaten) even more emphatically, a male will tap the ground with his legs and vibrate his abdomen in the spider equivalent of a floor-shaking drum solo. Although spiders lack ears, jumpers hear remarkably well, sensing vibrations up to 10 feet away through bristles on their bodies.

The female studies the male’s swagger and listens to his seismic signals for clues as to what kind of offspring he might produce. If she judges his efforts acceptable, she crouches down, vibrates her abdomen, or waves her legs to signal her peaceful intentions. Then the pair mates and, lest there be second thoughts about dinner, the male makes a hasty retreat.

The female forms a tent out of rolled up leaves and silk. Inside, she lays around 100 eggs — more or less, depending on the species — and encases them in a silken cocoon. Some species lay a single clutch; others lay multiple clutches. Most females guard their egg sacs until they hatch and then watch with oversized eyes as the little spiderlings wander away to take their first leaps.

Fear Not!

Jumping spiders are equipped with fangs and venom to subdue prey, but they’re not dangerous to anything bigger than a bug. They rarely bite people, and when they do, it usually results in nothing more than a mild sting or an itchy welt.

Show-Me Jumpers

Although most jumping spiders live in the tropics, plenty are found in higher latitudes. The American Arachnological Society estimates 344 species live in the U.S. and Canada, and 44 of them have been documented in the Show-Me State. It’s likely additional jumpers make their homes in Missouri, based on their occurrence in neighboring states. But because they’re small, secretive, and many look nearly identical to each other, some are probably overlooked. Here are a few common, colorful, or notable species to look for.

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Bold Jumper

Phidippus audax

Length: 6–19 millimeters

Where: Tree trunks, deck railings, rocky areas

The mouthparts of this large and common jumper are typically iridescent green.

Dimorphic Jumping Spider

Maevia inclemens

Length: 5–10 millimeters

Where: Forest edges, often on vines such as poison ivy

True to their name, males of this species occur in two forms: black or light gray. Both forms occur in relatively equal numbers, and females do not seem to prefer one form over the other.

Cardinal Jumper

Phidippus cardinalis

Length: 6–12 millimeters

Where: Prairies, weedy fields

Although cardinal jumpers are harmless, they look remarkably like velvet ants (cow killers), which can deliver an excruciating sting.

White-Jawed Jumping Spider

Hentzia mitrata

Length: 3–5 millimeters

Where: Forests

This tiny white jumper, named for its oversized mouthparts, is a canopy dweller, hunting in the uppermost reaches of trees.

Bandana Jumper

Habronattus coecatus

Length: 5–8 millimeters

Where: On the ground among sticks, rocks, or leaf litter

This species is named for the band of red scales on a male’s face. During courtship, males perform complex drum solos, which can consist of up to 20 distinct patterns.

High-Eyelashed Jumping Spider

Phidippus mystaceus

Length: 6–10 millimeters

Where: Backyards, forest edges

Long tufts of hairs on the “forehead” give this spider its common name. The tufts are more prominent on females.

Emerald Jumper

Paraphidippus aurantius

Length: 7–12 millimeters

Where: Woodlands, backyards, inside houses

This colorful jumper’s appearance is quite variable, but both males and females usually have green scales on their cephalothorax and abdomen that shine like emeralds.

Common Leaf-Beetle Jumper

Sassacus papenhoei

Length: 3–5 millimeters

Where: Dry grasslands

The shape and iridescent scales of this tiny jumper make it look nearly identical to shiny-shelled leaf beetles.

Ant Mimic Jumper

Synageles noxiosus

Length: 2–4 millimeters

Where: Fence posts, trees, stalks of upright vegetation

This jumper lifts its second pair of legs and waves them like antennae to better mimic ants.

From Fear to Fascination

Most folks spare little love for spiders. Indeed, in the pantheon of creatures with lopsided terror-to-threat ratios, spiders often crouch in their own dark chapel. But spiders in general, and jumpers in particular, are among the best creatures at curtailing truly harmful creepy-crawlies. In a 2017 paper published in The Science of Nature, European biologists estimated that the global spider population consumes 400 to 800 million metric tons of prey annually. Given that 90 percent of their prey has six legs and is weighed in milligrams rather than kilograms, that’s an unfathomable number of disease-carrying insects and agricultural pests that spiders remove — for free — from the environment.

Logic, however, is no match for one’s limbic system, and this article isn’t likely to mitigate anyone’s fear of spiders. But if you’re at a point where you want to overcome your arachnophobia, jumping spiders might be a good entry to a little exposure therapy. With their inquisitive eyes, bright colors, and furry bodies, salticids are among the most approachable of arachnids — the Labradoodles of the spider world. Watch one long enough — from a distance of course — and you might find your fear tip slightly toward fascination.

Also In This Issue

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Engelmann Woods NA
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Sometimes the best conservation areas are right in your own backyard

This Issue's Staff

Magazine Manager - Stephanie Thurber
Editor - Angie Daly Morfeld
Associate Editor - Larry Archer
Photography Editor – Ben Nickelson
Staff Writer - Kristie Hilgedick
Staff Writer - Joe Jerek
Staff Writer – Dianne Van Dien
Designer - Marci Porter
Photographer - Noppadol Paothong
Photographer - David Stonner
Circulation – Marcia Hale