Fright Week: Tarantula vs. Wasp

A nightmare battle, or strategic equilibrium? (Photo by Gail Karlsson)
A nightmare battle, or strategic equilibrium? (Photo by Gail Karlsson)

Spooky Halloween decorations might get you thinking about all the different spiders you have met up with. I certainly won’t forget the first time I saw a tarantula in St. John.

It was when my older son was two years old. Someone visiting us pointed out a big hairy spider crawling towards his crib. I didn’t know anything about tarantulas, but I bravely grabbed a broom and swept it briskly out the door. Later I learned that tarantulas sometimes stand up on their hind legs and fling needle-like hairs when they feel threatened. Fortunately, I have not experienced that.

­In the Virgin Islands the tarantulas are not particularly feared and are somewhat affectionately called “ground spiders.” They make quarter-sized holes in the yard and mostly stay inside their burrows below ground waiting for large insects like crickets and grasshoppers to stop by for dinner.

Sometimes a cat can be too curious. (Photo Gail Karlsson)
Sometimes a cat can be too curious. (Photo by Gail Karlsson)

The tarantulas do look scary, but I have never seen one be aggressive, even when the cat maybe got too close. Still, I don’t like finding them in the house. Or hiding in the shoes outside the door.

Be respectful of a tarantula on the doormat. (Photo Gail Karlsson)
Be respectful of a tarantula on the doormat. (Photo by Gail Karlsson)

A few years ago I discovered that the kids had learned at camp how to pull a tarantula out of its burrow. You stick a specially chosen grass stalk down the hole in the ground and wave it around until the tarantula gets annoyed and grabs on. Then you carefully tug on the piece of grass until the hairy spider comes into view. A fun trick to show island visitors.

However, I recently found out that tarantulas have to contend with much more terrible threats than bothersome children.

One morning after the weekly bird walk, I was walking with National Park Ranger Laurel Brannick over by the Annaberg ruins. On our way up the hill, there seemed to be a bunch of very fast-moving butterflies on the path, like a group had just hatched. When I got a closer look, they turned out not to be butterflies. “Tarantula Hawks,” said Laurel. Wasps, fierce ones.

They looked nice enough to me – blue-black with beautiful red wings – and they were peacefully flitting around in the flowers, drinking nectar and hanging out with the ladybugs.

This Tarantula Hawk wasp seemed to be patting a cute ladybug on the head. (Photo Gail Karlsson)
This Tarantula Hawk wasp seemed to be patting a cute ladybug on the head. (Photo by Gail Karlsson)

But the story Laurel told me was not a pretty one.

It seems that when the female wasp is ready to start a family, she has a gruesome way of providing food for the emerging larvae. She finds a tarantula hole and pokes around the opening, where the spider sets silk traps for its prey. When the tarantula comes up to investigate, she grapples with it, stings it and paralyzes it. Then she drags it back into the burrow, lays one egg on top of the immobilized tarantula, crawls out, and covers up the burrow hole to seal it. When the wasp larva emerges from the egg, it has a captive, paralyzed tarantula to feed on. Just before it leaves the burrow as an adult, the young wasp eats the tarantula’s heart and ends its misery.

Wow. Besides being gruesome, that seems like a lot of work – and food – for just one egg. One dead tarantula for every new Tarantula Hawk. Given the number of wasps flying around that afternoon, I was shocked to think about how many poor tarantulas must have been entombed on that small hillside. Could there really be so many victims under there? And then how many more live ones?

I read that the Tarantula Hawks have very short lives, only a few weeks or months, even though predators leave them alone because they don’t want to get stung.

A Tarantula Hawk wasp gets nectar from a flower. (Photo Gail Karlsson)
A Tarantula Hawk wasp gets nectar from a flower. (Photo by Gail Karlsson)

Meanwhile, a female tarantula can live for up to 20 years – if she doesn’t get attacked by one of those wasps. How can the tarantulas sustain big losses in their numbers and still maintain their own continuity?

I began thinking that there must be some complex evolutionary balance between these enemies to allow both species to thrive. But maybe it’s just that female tarantulas can produce hundreds of eggs at a time. Then I started imagining how many tarantula burrows there would have to be to house them all. All of a sudden, the ground started feeling a lot less solid!

Spooky indeed.

Gail Karlsson is an environmental lawyer, writer and photographer – author of “The Wild Life in an Island House,” plus the guide book “Learning About Trees and Plants – A Project of the Unitarian Universalist Fellowship of St. John.” See and Follow her on Instagram @gailkarlsson