The Wasp and the Caterpillar

Top Photo: caterpillar lying on its side next to burrow entrance.

As I walked past the Pollinator Garden which is just above the Butterfly House Rain Garden, I notice a green object hurriedly angling across the path. It looked like a caterpillar, but it had an odd movement, a side to side wiggle, and speed which most caterpillars don’t display while moving along the ground, or anywhere else. There are a handful of swift moving caterpillars, but none quite this fast, and none with a side to side wiggle.

Grabbing my camera, and moving in for a closer look, I realized it was a wasp, a thread-wasted wasp dragging its prey beneath its body and between its long legs. It was most certainly racing off with a paralyzed caterpillar to stock its nesting burrow.

I couldn’t mobilize my camera quick enough to get a shot of the wasp actually hauling the caterpillar, it was too swift and disappeared into a stand of sweet pepper bush alongside the path. I’ll never find it now.

I was wrong. I lucked out. The wasp had dropped the caterpillar only inches inside the cover of the pepperbush and I quickly located it, the caterpillar that is. The wasp had vanished. I fired off a flurry of shots with the camera (top photo).

Seconds later the wasp reappeared. It had been in the burrow which I at first hadn’t noticed until the wasp resurfaced. It was in the burrow to clear the way for the caterpillar who was now lying on its side beside the entrance.

Wasp entering burrow to clear way for caterpillar.

The wasp digs a burrow to nest in, then flies off to capture prey. While gone, the wasp places dirt balls, pebbles, or other debris in front of the entrance to conceal and discourage other wasps or insects from entering the burrow.

This particular wasp looks to be Eremnophila aureonotata, a widespread thread-wasted wasp. The white spots on the side of her thorax are distinctive. The wasp digs burrows into sandy or loamy soil, and stocks the burrow with a single paralyzed caterpillar. She then lays a single egg in the burrow and covers it with dirt or sand and flies off.

When the wasp egg hatches the larva will slowly consume the still alive but immobile caterpillar, pupate and emerge an adult wasp the following spring.

White marks on side of thorax indicate this is Eremnophila aureonotata.

These long-legged and long bodied wasps often visit flowers to sip nectar. I frequently see them at mountain mint in the pollinator garden.

Several more trips inside the burrow and the wasp grabbed the caterpillar by its head and pulled it in behind itself.

Prepping for the drag into burrow.
Wasp has backed into burrow and has grasped caterpillar by head.
And down it goes.

There must be a large hollowed-out chamber within the burrow to allow for the wasp to pass by the caterpillar on the way out. It seemed a tight fit going in.

The unfortunate caterpillar appears to have been a variable oakleaf prominent. The caterpillar is variable in color and can be confused with the double-lined prominent. I’m basing my opinion of its identity on the width of the white stripe next to the black mark on the face of the caterpillar which, according to references consulted, is supposed to be wider in variable oakleaf prominent than double-lined.

You never know what will turn up on a walk in the outdoors.

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