Thursday, September 3, 2009

Tarantula Hairs

--- Notice the red hairs on the tarantula's abdomen. ---

I was driving a hot country road one evening last week. 96 degrees Fahrenheit and I thought the road was melting. Until I saw a tar bubble move. It was a tarantula crossing the road. Screeeech, I pulled over at the next curve, grabbed my camera, and ran back.

--- Hazards of Page Mill Road ---

Recently, I've noticed two peculiar holes in the ground next to the red barn at the Dipper Ranch. They are about one inch in diameter with a silky carpet that drapes over the lip and lines the inside. I had a vague recollection that these might be tarantula lairs. When I peeked in the holes, day or night, and gently poked around with a grass stem, I was unable to stir up a resident.

--- Possibly a tarantula hole ---

So, I was excited to follow the real 8-legged critter, even if it was taking its time to cross the hot asphalt. After waving a car full of chattering boys around the beast, I nudged Mr. Hairy Legs with a long stick to the road shoulder, a safer place for the legs, my camera and curiosity.

--- Run faster! ---

When the tarantula paused on the grass, I walked around to photograph it from the front side. It raised its abdomen. I wasn't sure what that meant, but since its fangs were on the ground side of its body, I didn't worry too much. Eventually it trundled off into the grasslands and I headed back to the car. I crossed the road for a safer line-of-sight, only to find another tarantula on that side of the road. As the sun set, I got a few photographs of the second tarantula. Figuring it was a good night for sightings, I shined a flashlight down the barnside holes when I got home, but still, no Dipper tarantulas revealed themselves.

I've also been on the alert for tarantulas since spotting several tarantula hawks in the last few weeks. Tarantula hawks are large, colorful wasps that prey on tarantulas. They sting a tarantula, drag it down a hole, lay one egg on its body, and the larvae hatches and eats away at the paralyzed spider.

[Can't find my tarantula hawk photo. Do you have one? The ones we have in coastal central California are black-blue body with orange wings.]
New photo of tarantula hawk added on next day.

Since my tarantula adventures the other night, I've researched tarantula behavior. I am less scared of them now, but advise more caution because of some of their peculiar, dare I say hairy, behavior. I think the roadside tarantulas were Aphonopelma iodius because this species has a dark triangular patch around the cluster of eyes at the front of its head, and it is widespread in California. These were probably males which leave their burrows this time of year to search for female mates.

Tarantulas otherwise spend most of their time in their burrows, and through vibrations transmitted by the webbed collar, they detect the outside passing of insects or other small prey. Then, they dash out of the burrow, sink their fangs into the prey and inject a venom which paralyzes and prepares it for spider digestion. We hear wild stories about the tarantula's bite, but all the tarantulas in the United States have a bite similar do that of a wasp or bee.

--- Preparing for hair warfare? The black triangle marks this species' compound eyes. ---

Tarantulas have an unusual defense against larger creatures attacking them - they throw hair. Many tarantula species have hairs on their abdomen that are barbed and mildly venomous. If a mouse or skunk gets too close, the tarantula will press or use its legs to throw these hairs into the face of the threatening animal where they irritate the sensitive mouth, nose and eye tissues. So, maybe Mr. Hairy Legs was raising his abdomen at me in preparation for hair warfare. Fortunately, I was using a long lens on my camera and did not get too close. I advise you don't get within hair throwing distance of tarantulas.

---Short tibial hook on male tarantula.---

Male tarantulas have a spur on the front pair of their walking legs (tibial hooks) which they use to keep the female's fangs out of the way while they mate frontside. I won't go into tarantula mating behavior further; here's a link.

--- Second tarantula showing his pedipalps between front legs
and distinct red hairs on his abdomen.---

I've read that male tarantulas use their pedipalps (shorter leglike appendages near the mouth mostly for handling food) to drum on the webbing outside the female tarantula's burrow. If the beat is right and the female is receptive, then spider nightlife . . . well, see link above.

This explains a mystery I have pondered for many years. Once I took a hike with a friend in Pinnacles National Monument. This friend repeatedly pointed out tarantula holes. When we challenged his claims (afterall, he was an ornithologist), he said he could prove it. At the next silk-lined hole, he carefully stripped a grass stem and gently lowered it into the hole. As he pulled the stem out, there was a tarantula clinging to it. To the delight of the kids, he was able to repeat this magic trick at four more consecutive holes, however, none of us could do it. I always thought he was getting the spider to grasp the stem out of irritation. Now I realized he must have known the tarantula mating drumbeat. I wonder what ever happened to that guy.

See also:

American Tarantula Society

ENature article on tarantulas

ENature article on "Spittin Hairs"

Basic tarantula facts from desert website

Tarantulas at the Beetles In the Bush blog


  1. Sheesh, tarantulas already? Where does the time go???

    I didn't know about the hair throwing, and before I was on my current kick of teaching myself to be more polite to wildlife, I loved tickling their back legs so they would shake their front fist at me, á la "get outta here, crazy lady!"

  2. I would love to learn the drumbeat and grass stem trick.

    Aren't the Pinnacles a fabulous place?!


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