Alamogordo New Mexico, United States 5 Oct 10
Odometer 69,898 m 112,490 km

Why did the chicken cross the road? Mankind has been asking this seminal question since the first roads were built. But a more important question might be: why does human curiosity extend only to jaywalking fowl? Why aren’t, say, tarantulas just as intriguing? After all, they cross the road in legions, yet nobody seems to see any humor in that.

The theraphosids, or tarantula family, get their name from the southern Italian town of Taranto, where Europeans originally mistook their local wolf spider as belonging to this group. There have since been 900 species of tarantulas described worldwide, all similarly large, hairy and ferocious-looking, despite their rather gentle demeanor.
tarantula migration
Common name: Oklahoma brown tarantula, mature male
Aphonopelma hentzi
Family: Theraphosidae (tarantulas)
Order: Araneae (spiders)
Class: Arachnida (spiders, mites, scorpions)
Phylum: Arthropoda (spiders, insects, crustaceans)
Tarantulas are arthropods, like crabs. This means they’re supported not by a spine and bones, but by an exoskeleton that must be shed in order for them to grow larger. But tarantulas are also spiders, the largest order of arachnids, defined by the eight legs on which they crawl about. Their large, furry bodies are divided into two parts: the cephalothorax, which includes the head and is the part to which the legs attach; and the abdomen, or rear, which is covered with porcupine-like, barbed hairs designed to sting the eyes and nose of attacking predators.

Meat eaters, tarantulas of the southwestern United States hunt at night by lying in wait near the opening of their well-disguised, subterranean burrows. When a cricket or similar insect gets within a few inches (8 cm), the spider leaps out, bites its prey with venomous fangs, then drags it back down into its burrow. The venom liquefies the victim, allowing the tarantula to suck it dry for nutrients.

Female tarantulas tend to be somewhat larger than males and can live to be 20-plus years old. They spend nearly all of that time alone within the foot-deep (20 cm) burrow that they themselves excavate. She’ll lay about 100 eggs atop a sheet of silk spun from her spinnerets, usually in June, which hatch after two months of near constant care. The spiderlings don’t stick around for long, though, soon dispersing on foot to establish their own burrows. The survival rate is low: out of each brood, only one or two offspring typically make it to adulthood.

Male tarantulas also live solitary lives, hunting for food from within their burrows until about the age of seven, when with their final molt they reach maturity. At that point they strike out--leaving home for the
first and last time--on a single-purpose mission to locate their female counterparts. It is this swarm of lovelorn males, searching for paramours they’ve never before laid their eight eyes on, that form the annual tarantula migration.
More charismatic migratory species are well known to most people: wildebeest and bison, geese, cranes and monarch butterflies, whales and salmon. They’ve all evolved strategies to chase the availability of resources from one place to another. But unlike those in search of greener pastures, warmer weather, or calmer waters, migrating tarantulas have only one thing in mind: girls.

Obviously, male maturity brings with it a newfound friskiness. Less obvious are two ways in which their body's transform to assist the endeavor. First, their legs grow longer; instead of just climbing in and out of their burrows, they now must walk for great distances. Second, they grow little stirrups on their two front legs with which they restrain the dangerous fangs of the female tarantula while mating.

Post copulation, the male quickly unhooks his stirrups and beats feet out of Dodge before his mistress gets the munchies (though not common, females have been known to devour their mates). He’ll then march on in search of further exploits before ultimately succumbing to fatigue and winter weather.

This roving romp-about is brief, lasting only a month or two, and filled with peril beyond that posed by the opposite sex. Tarantulas are large, slow-moving and easy-to-spot targets. Many predators consider them an annual delicacy. But no bobcat, coyote, lizard or bird can come close to matching the lethality leveled by one particular nemesis: the
tarantula hawk.

These huge, black and orange spider wasps of the Pompilidae family dine on tarantulas in a way normally reserved for overly imaginative horror flicks. It begins when the female hawk’s aerial surveillance pinpoints a wandering male tarantula. She then aggressively flies in on the attack, resulting in a spectacular scuffle.

One sting is all it takes to paralyze her prey--she must take him alive--but his natural defenses are only penetrable within a small, vulnerable area beneath each leg. In the battle royale that I witnessed, the wasp emerged victorious. The tarantula, losing its mobility, was then dragged to a nearby crevice by the female hawk, who then laid a single egg upon his body and buried him alive to serve as living flesh for her larvae to consume!

Clearly, the final days of love struck male tarantulas are not all hanky-panky. They’ve been holed up for seven long years. They emerge for what will be their last hurrah, their day in the sun, their singular opportunity to find romance. Then, if they aren’t consumed by their mates, hunted down by predators or paralyzed by tarantula hawks--they’re simply run over by careless drivers.

Why did the chicken cross the road? We may never know, for sure. But we do know our eight-legged friends do it for love.

So, have a heart. Slow down. And give the poor guys a brake.

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