Attention arachnophobes: You might want to avoid the Eastern Plains of Colorado in the fall.
Each year as foliage is turning, spiders come out on bleak sections of highway near Ordway, Olney Springs, Boone, Sugar City and La Junta. Big, hairy spiders. Tarantulas. Hundreds of them trek across highways in migratory waves as they search frantically for mates.
Beginning in mid-September and tapering off now, the spiders try to eight-leg it across the busier and dicier roads east of Pueblo and creep their way through the Comanche National Grassland.
“People around here look forward to it. And they kind of take it for granted,” said Ordway resident Mary Beth Tucker, who has been observing the tarantula migration for a lifetime.
When Tucker was still in grade school, the driver of the little yellow school bus would occasionally stop to let the kids ogle the hundreds of tarantulas crossing Colorado 71.
The older boys would be allowed off the bus to capture some in glass jars for show and tell. Tucker said the younger boys would roll down the windows and “ooh” and “ahh” while the girls would shrink back and “eek” over the hairy waving legs outside the bus.
The “eeks” weren’t for real. Folks around the Eastern Plains know that the fanged spiders really aren’t poisonous and can only irritate human skin by throwing off darted abdominal hairs.
Colorado State University entomologist Whitney Cranshaw has been travelling to the plains for three decades to witness the annual migration and collect specimens. His explanation for the most visible part of the migratory phenomenon sounds like a chicken joke.
“They don’t particularly like roads. They are just crossing them to get to the other side,” he said.
In more scientific terms, Cranshaw explained that the spiders, which are of the Oklahoma brown variety, are common in southeast Colorado because the females like to make their burrows in undisturbed prairie rangeland. Those females then stick close to their burrows for the entirety of lives, which can be 25 years long.
The male tarantulas — when they reach about 8 years old, or turn into “young bucks” in Cranshaw’s term — gang up in groups and set out, using their senses of touch and vibration to locate the ladies.
They tend to turn up in waves on specific spots on highways because of where female burrows are. The burrows can be located in strips of unplowed ground between cultivated fields. So adjacent sections of roads attract tarantula traffic jams.
The male tarantulas must dodge the tractor-trailers, school buses and giant-wheeled farm implements on their trek to these burrows, but they are doomed anyway. One bout of sexy time and the males die.
Around Otero, Crowley, Bent and Kiowa counties, folks know it’s spider migration time when the foliage starts changing colors. And nowadays, when they read about it on Facebook posts.
You’ll see comments like, “Oh, it must be fall, the spiders are out.”
Cranshaw has another way of telling when the spiders are starting to get motivated by that lovin’ feeling. He watches for tarantula hawks — really not hawks at all, but wasps.
These large blue-bodied, orange-winged wasps are the only natural predator of tarantulas, and they will be buzzing around when tarantulas are on the move.
What they do to tarantulas would really make the girls on the bus go “eek.”
These gaudy wasps sting tarantulas to paralyze them, pull them into a crevasse and then lay eggs on the immobilized spiders. When the eggs hatch in three or four days, the wasp larvae feed on the helpless live tarantulas. They save the vital organs for last so that their hosts won’t miss any of the feasting torture.
It’s that kind of fascinating tarantula-related fact that prompts Cranshaw to exclaim, “Southeast Colorado has the best bugs in the state!”
Nancy Lofholm: 970-256-1957, nlofholm@denverpost.com or twitter.com/nlofholm
