Watching a Spider Wasp Hunting in Southwestern Colorado

Photos and text from an afternoon spent watching a Pompilid Spider Wasp catching a Spider in Southwestern Colorado.
Photo of pompilid spider wasp carrying her paralyzed spider victim
The Spider Wasp retrieving her paralyzed victim’s body.

A few days ago (November 11, 2024), I was sitting in the backyard, watching birds and reading. I noticed a black wasp moving over the ground. The wasp was small, only about 10 mm long. It would run a short distance, fly a foot or so, pause, then repeat. It would twitch its wings nervously every five or 10 seconds.

I got on my hands and knees, and slowly crept forward to get a better look at it. No luck! The wasp would flit away whenever I got within three or four feet. Instead, I tried watching the wasp from further away, using my camera’s long telephoto lens. That seemed to work. These images are mostly cropped from my 600mm telephoto lens, taken from seven or eight feet away.

This looked to be a Spider Wasp – a member of the family Pompilidae. Most of these wasps hunt spiders. When they find a spider, they’ll paralyze the it with a precisely placed sting, then lay an egg on the paralyzed spider. The egg hatches, and the larva consumes the spider, pupates, and emerges as an adult Spider Wasp.

Since this wasp appeared to be hunting, she was a female. Males typically don’t hunt, since they don’t lay eggs.

The Initial Excavation

Now that I was further away, my wasp settled down. She would disappear under a rock for a while, then emerge carrying a clump of dirt in her jaws, as in the photo below.

A Pompilid Spider Wasp excavating soil from beneath a rock.
A Pompilid Spider Wasp excavating soil from beneath a rock.

She dug beneath the left side of the rock for five minutes or so. Then she walked over to the other side of the rock and dug some more. Were these all contiguous excavations, or were they separate chambers? I’m not sure. I didn’t see her crawl under the rock from one side to the other, so suspect they holes weren’t contiguous.

A Pompilid Spider Wasp excavating soil from beneath a rock.
A Pompilid Spider Wasp excavating soil from beneath a rock. She’s pulling out chunks of compacted soil grains with her mandibles.
A Pompilid Spider Wasp excavating soil from beneath a rock.
Another shot of a Pompilid Spider Wasp excavating soil from beneath a rock.
A Pompilid Spider Wasp excavating soil from beneath a rock. Each chunk she is excavating is relatively enormous.
A Pompilid Spider Wasp excavating soil from beneath a rock. Each chunk she is excavating is relatively enormous, it looks almost as large as her.

After 15 minutes or so of digging on the right-hand side of the rock, she walked about a foot away from the rock. She paused to groom herself on some dead Cottonwood leaves.

She left the excavation after digging for 15 minutes or so.
She left the excavation after digging for 15 minutes or so.
She paused on this fallen Cottonwood leaf for a few seconds, then continued running.
She paused on this fallen Cottonwood leaf for a few seconds, then continued running.

The she ran another foot or two, stopping at yet another hole in the ground. This one was between two clumps of hardened mud. Through the telephoto lens I could see that the hole was surrounded by webbing.

Was this a spider hole, and the wasp was hunting?

The Hunt

She walked around and around the hole entrance, tugging at it with her mandibles. Sometimes she would go partially into the hole, then come back out, then pull and dig at the hole entrance some more.

Eventually, she came to a gap between two rocks. The gap was partially shrouded in webbing.
Eventually, she came to a gap between two rocks. The gap was partially shrouded in webbing.
She began pulling at the webbing, as if she were trying to dig through it.
She began pulling at the webbing, as if she were trying to dig through it.

She’d go further and further into the hole as she pulled openings into the webbing. I’d just see the tip of her gaster protruding from the hole.

Eventually, she managed to get all the way into the hole. When she had disappeared completely, a young Scleropus lizard darted forward and stared intently at the opening.

She began pulling at the webbing, as if she were trying to dig through it.
She began pulling at the webbing, as if she were trying to dig through it.

The lizard stayed, staring at the hole, for a few minutes, while the wasp was fully inside. Then the wasp came back out, the lizard gave me a glance, and then walked away.

After a few minutes, the wasp re-emerged from the tunnel, with the lizard watching.
After a few minutes, the wasp re-emerged from the tunnel, with the lizard watching. The lizard wandered off after the wasp came out.

I had assumed that the lizard was waiting to ambush the wasp. Since the lizard calmly left when the wasp came out, now I wonder if the lizard was waiting to see if a spider came running out of the hole.

Or, perhaps the lizard was just attracted by the commotion and left when it saw the wasp.

Now the wasp went partially back into the hole. She just had the tip of her gaster out of the hole again.

The wasp returned to the fissure many times, pulling and tugging at something.
The wasp returned to the fissure many times, pulling and tugging at something.
The wasp would dig and pull inside the hole. She would come out every couple of minutes, look around, then return to the hole.
The wasp would dig and pull inside the hole. She would come out every couple of minutes, look around, then return to the hole.

She’d pull and tug and work at something that I couldn’t quite see. Eventually, she had tugged away most of the webbing, and the hole was quite wide.

The wasp eventually had cleared away much of the webbing at the fissure entrance. Still she struggled with something inside the hole.
The wasp eventually had cleared away much of the webbing at the fissure entrance. Still she struggled with something inside the hole.

After a few more minutes of tugging and working, I could see a spider. The spider’s limp body was an awkward dead weight, getting snagged on every obstacle as the wasp pulled at it.

The wasp eventually dragged a paralyzed spider to entrance of the hole.
The wasp eventually dragged a paralyzed spider to entrance of the hole.
The spider was still stuck in the hole entrance. The wasp twisted, turned and pulled at the spider's body, trying to get it past hang-ups in the rock.
The spider was still stuck in the hole entrance. The wasp twisted, turned and pulled at the spider’s body, trying to get it past hang-ups in the rock.
Success! And a Strange Side Journey

Finally, the spider’s paralyzed body popped out of the hole. I think this was a Ground Spider – a member of the spider family Gnaphosidae. It could also be a Wolf Spider of some kind.

After the wasp pulled the spider free of the hole, she excitedly mouthed the spider’s legs while turning the spider’s body round and round, as though she could not believe her luck.

Eventually the wasp pulled the paralyzed spider free of the hole.
Pompilid Spider Wasp and spider prey.
The wasp spent several minutes mouthing the spider’s trochanters, the bases of its legs.

Eventually, she grabbed one of the spider’s hind legs and began to walk backwards, pulling the spider along behind her.

Pompilid spider wasp dragging spider prey
The wasp grabbed the spider and dragged it away from the burrow.

She pulled the spider up a fairly steep incline, away from the spider’s hole.

Pompilid Spider Wasp dragging spider prey.
The wasp was dragging the spider’s body up a fairly steep incline.
Photo of Pompilid Spider Wasp dragging spider prey.
The wasp was dragging the spider’s body up a fairly steep incline.

She seemed to make her best progress when the spider was sledding along on its back. If the spider caught on a snag and flipped over onto its belly, the wasp had a hard time pulling the spider. She’d tug and work at the spider until it was over on its back again.

Photo of Pompilid Spider Wasp dragging spider prey.
The body of the spider would awkwardly snag on outcroppings of soil as the wasp dragged it up the incline.
The Spider Wasp continued dragging her prey up the slope. She was about 5-6 feet away from the Spider’s lair at this point.

She kept pulling up the slope until she reached a near vertical part of the slope, then left the spider on a small ledge there. She was perhaps 4 feet away from the spider’s burrow, and maybe eight vertical inches above it.

Photo of pompilid spider wasp and her spider victim.
Finally, the Wasp dragged her spider prey to a small alcove, then left it. You can see the paralyzed spider in the upper left corner of this photo, in the shade.

Then the wasp walked a few inches away, leaving the spider on the ledge, legs limply sprawling. The wasp stopped in the sun and waited for a few minutes. Was she resting? Thinking? Re-orienting? I don’t know.

Back to the Initial Excavation!

She walked back up to the ledge and grabbed the spider by one of its legs, and dragged the body back down the slope.

The Spider Wasp retrieving her paralyzed victim's body.
The Spider Wasp retrieving her paralyzed victim’s body.

She quickly dragged the spider more-or-less directly back to the rock where I’d first seen her excavating(!) This surprised me, because she had originally been carrying the spider away from that initial excavation.

When she got back to the initial excavation site, she dragged the spider up under the rock, at the location where she had been digging earlier. I didn’t see her again after that.

Here’s a photo of the general area of the action. I was sitting on the stone bench, and the spider’s initial excavation was at the position indicated by the red arrow.

Photo of my 'office'
My “office” – I sat on the stone bench at the left. The red arrow indicates approximately where the Spider Wasp was hunting.
So…What happened here?

The chronology was:

  • The wasp excavated a hole
  • She walked a couple of feet to the spider’s hole, dug out the spider
  • She dragged the spider uphill and away from both the initial excavation and the spider’s hole
  • She left her spider on a small ledge while she sat in the sun for a while
  • She dragged her spider back down the slope, on a nearly direct route to the initially excavated hole
  • She dragged her spider under the initial rock

Here’s my speculation regarding what went on.

  • I think the wasp located the spider before I began watching. I think she paralyzed the spider at this point, and then the wasp left the spider.
  • Now that she had a spider, she dug a nest burrow under the rock.
  • Then she went back to the spider’s burrow and dragged it out of the burrow. She may have paralyzed it at this point, if she hadn’t paralyzed it initially

So why, at this point, did the wasp drag the spider away from both the spider hole and the initially excavated burrow? I don’t know! Perhaps she was disoriented, and she regained her bearings during that time in the sun?

Here’s something I wonder about, though.

Some insects – flies, other wasps, etc – forgo the danger and difficulty of capturing their own prey. These are ‘kleptoparasties’ – thieves. One variation of their behavior is that they will follow hunters such as our intrepid Spider Wasp, then surreptitiously lay their eggs on our wasp’s prey. The wasp doesn’t realize that the spider has the kleptoparasite’s eggs on it, so she takes the spider back to her nest burrow.

The kleptoparasite eggs hatch, and their larvae will eat Spider Wasp’s prey…and perhaps even the Spider Wasp’s larva, as well.

I wonder if the Spider Wasp was waiting, looking to see if there were kleptoparasites nearby?

Again, I don’t know.

But what a fascinating afternoon this was.

Sources

Marshall, Stephen A. 2023. Hymenoptera: The Natural History and Diversity of Wasps, Bees and Ants. Firefly Books (April 1, 2023). 640 pages. ISBN 0228103711. ISBN-13: 978-0228103714.

Nastasi, Louis F., R. Luke Kresslein, Kendick O. Fower and Sofia R. Fernández Flores. 2023. WaspID Course Manual – Biodiversity & Classification of Wasps. Downloadable PDF, released under Creative Commons license. DOI:10.26207/ax00-rk88

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