…most will be murderesses, but they have brought murder to a fine art, an act of exquisite precision.

~John Crompton, introduction to his book, The Hunting Wasp

Rusty spider hunter wasp with prey (click photo to enlarge)

As we were starting to get into the car last weekend at my folks’ place, I saw some movement on the driveway. A closer look reveled a large wasp dragging a spider rapidly across the surface. By the time I got the camera out of the car, the wasp had carried her load another few feet. As I leaned in for a photo, she dropped her prize and scurried toward the garage door, circling as if looking for something. I have seen this behavior many times with this group of wasps, the spider hunters in the family Pompilidae.

Adult spider hunters feed on nectar, but females provision their nest with a paralyzed spider for their young. The wasp precisely stings a spider (often one that is much larger than herself) to stun it, not kill it (the developing larva needs “fresh” food, not a rotting spider corpse). Grasping the spider by the pedipalps or chelicerae, she then walks backwards, dragging her prey to a nest cavity she has already dug. If disturbed, she may drop the spider and return later to continue her labors. She may also occasionally drop the spider and scout ahead for the exact location of her burrow, which, as she gets close, she hones in on based on visual landmarks near the entrance hole.

We watched as the wasp disappeared with the spider into a hole in a crack where the pavement met the building. This is a common location for burrows of this species, the rusty spider hunter, Tachypompilus ferrugineus. In most species of spider hunters, the single egg laid on the spiders’ abdomen will hatch in about 10 days. The wasp larva eats the non-vital tissues of the stunned spider first in order to keep its meal as fresh as possible while it feasts. After completing its meal, the wasp larva spins a cocoon and pupates. One researcher reported that the size of the spider may determine the resulting sex of the developing wasp larva, with larger prey leading to female wasps. Rumor has it that many of the spider hunters can inflict a painful sting if grabbed by a careless human, but this female was busy with her provisioning and paid us no mind. We felt lucky to witness one of nature’s classic scenes of life and death in the asphalt jungle of a driveway. You just never know when or where nature will reveal some of her mystery…