I have a Chalet A-frame folding camper and took it with me on two of my trips to Lake Tawakoni State Park. One time on my way to the park I stopped at a gas station and noticed an orb web on the back of the trailer, attached to the bumper. Amazingly, the highway wind had not destroyed the web. The poor owner, a hackle-band orbweaver (family Uloboridae), cuddled closely to the bumper, hanging on tightly.

When I arrived at the park six hours later, her web had shrunk to nothing but a single line of heavy thread. But she was still there, clinging dearly to the bumper. She rebuilt her web during my stay at the park. I left her on the camper, hoping I could take her back home, and indeed, she clung to the bumper all the way back as well. She disappeared a few weeks later, as typically happens with adult orbweavers late in the year, leaving a series of egg sacs behind.

Unfortunately, when I visited her web again last week, this is what I saw:

A pirate spider (family Mimetidae) was raiding her egg sacs. I knew that pirate spiders ate other spiders, but I didn’t know that they would prey on egg sacs as well. Baby spiders hatch in the egg sacs and live on yolk until their first molt, so it’s possible that this pirate spider was actually eating young spiders rather than eggs. Still, the spider somehow knew to go after egg sacs and not just live, wiggly spiders.

Has anyone ever seen this before?