Sphex ichneumoneus, the great golden digger wasp, about to enter her burrow.
The sheltered gravel/sand area outside Higley Hall at Kenyon College is the perfect burrow building habitat for the great golden digger wasp.
Investment and return
Over six breeding seasons in the 1970s, H. Jane Brockmann recorded data of wasp behavior from three sites. Typically, each female will work on her own to dig and provision her burrow, but sometimes two females will begin provisioning the same nest in 5-15% of cases. The interloper takes advantage of the other wasp's spent investment and the two will be bringing katydids into the same nest. But because they spend most of their time away from the nest seeking new prey, it is only a coincidence if the two meet and fight over the nest. Fights last between 2 and 16 minutes and often the loser would leave and never return. Because of this one-on-one interaction where both insects have varying degrees of past interest (their future interests would be identical), the data can be thought of in simple game theory mechanics. The founding wasp took the time to dig the burrow and begin provisioning it, while the joiner risked being discovered and the subsequent fight to cheat and not build her own burrow. When faced with a fight, however, each has the same prize and motivation: a well-provisioned nest is worth fighting for, saving the winner days more of additional digging and hunting to lay a single egg.
The "sunk cost fallacy," or Concorde fallacy, so named because the British and
Number of katydids each fight participant brought. Nine fights were over empty burrows. From Dawkins & Brockmann, 1980.
Just one more quick interesting note about these creatures. In Daniel Dennett's book Elbow Room, he reproduces an account by Woolridge in 1963 about the deterministic behavior of Sphex ichneumoneus. Woolridge watched the wasps return to their burrows with katydids, leaving them just outside while they went inside to inspect. Normally, the wasp is inside for a few seconds, then reemerges and drags the paralyzed katydid backward down into the burrow. He decided to alter the pattern to see if the wasp's behavior changed. When the wasp entered the burrow, Woolridge would subtly move the katydid a few inches from the burrow threshold. The wasp reemerged to find he prey moved, dragged it back to the threshold, then dove back into the burrow alone to inspect again. Woolridge writes, "On one occasion this procedure was repeated forty times, always with the same result." The wasp appears to be an unwilling participant in a free will experiment. She is not a free agent, but instead is driven by environmental cues: once a katydid is near the threshold, I must inspect the burrow and only then can I bring it inside. This property, an apparent lack of free will, was even given the name sphexishness. Dennett notes that publications on free will are rife with fears of sphexishness. Call it genetic determinism or a behavioral loop. Perhaps, though, we're all a little sphexish.
And what of the wasps?
I know their short adult lives will be over soon, but I've enjoyed viewing them through the window these past few weeks. Apparently, though, their lives were meant to be shorter than usual. I walked out the door the other day and noted the acrid smell of pesticides on the air. It got stronger as I approached the burrows and each hole was wet, as if it had been sprayed. Sphex ichneumoneus is a solitary wasp that is not inclined to sting anything but katydids. If you approach them or their burrows, they fly away, bothering no one. I was told our department administrative assistant tried to fill the holes in one day and I suspect she alerted the maintenance department to their presence, thus leading to their demise. Perhaps if people took the time to find out more about the supposed threat before eradicating it, they might change their minds about the course of action. That at least one good motivation for effective science education.
DAWKINS, R., & BROCKMANN, H. (1980). Do digger wasps commit the concorde fallacy? Animal Behaviour, 28 (3), 892-896 DOI: 10.1016/S0003-3472(80)80149-7