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Sphex pensylvanicus on a katydid
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Suborder: Apocrita
Superfamily: Apoidea
Family: Sphecidae
Subfamily: Sphecinae
Genus: Sphex
Linnaeus, 1758
Type species
Sphex flavipennis
Fabricius, 1793

More than 130; see text

Wasps of the genus Sphex (commonly known as digger wasps) are cosmopolitan predators that sting and paralyze prey insects. Sphex is one of many genera in the old digger wasp family Sphecidae (sensu lato), though most apart from the Sphecinae have now been moved to the family Crabronidae.[1] There are over 130 known Sphex species.


In preparation for egg laying, they construct a protected "nest" (some species dig nests in the ground, while others use pre-existing holes) and then stock it with captured insects. Typically, the prey are left alive, but paralyzed by wasp toxins. The wasps lay their eggs in the provisioned nest and the wasp larvae feed on the paralyzed insects as they develop.

The great golden digger wasp (Sphex ichneumoneus) is found in North America. The developing wasps spend the winter in their nest. When the new generation of adults emerge, they contain the genetically programmed behaviors required to carry out another season of nest building. During the summer, a female might build as many as six nests, each with several compartments for her eggs. The building and provisioning of the nests takes place in a stereotypical, step-by-step fashion.

Sphex has been shown, as in some Jean-Henri Fabre studies,[2] not to count how many crickets it collects for its nest. Although the wasp instinctively searches for four crickets, it cannot take into account a lost cricket, whether the cricket has been lost to ants or flies or simply been misplaced. Sphex drags its cricket prey towards its burrow by the antennae; if the antennae of the cricket are cut off, the wasp would not think to continue to pull its prey by a leg.

The navigation abilities of Sphex were studied by the ethologist Niko Tinbergen.[3] Richard Dawkins and Jane Brockmann later studied female rivalry over nesting holes in Sphex ichneumoneus.[4]

Use in philosophy[edit]

Some writers in the philosophy of mind, most notably Daniel Dennett, have cited Sphex's behavior for their arguments about human and animal free will.[5]

Some Sphex wasps drop a paralyzed insect near the opening of the nest. Before taking provisions into the nest, the Sphex first inspects the nest, leaving the prey outside. During the inspection, an experimenter can move the prey a few inches away from the opening. When the Sphex emerges from the nest ready to drag in the prey, it finds the prey missing. The Sphex quickly locates the moved prey, but now its behavioral "program" has been reset. After dragging the prey back to the opening of the nest, once again the Sphex is compelled to inspect the nest, so the prey is again dropped and left outside during another stereotypical inspection of the nest. This iteration can be repeated several times without the Sphex changing its sequence; by some accounts, endlessly. Dennett's argument quotes an account of Sphex behavior from Dean Wooldridge's Machinery of the Brain (1963).[6] Douglas Hofstadter[7] and Daniel Dennett[8] have used this mechanistic behavior as an example of how seemingly thoughtful behavior can actually be quite mindless, the opposite of free will (or, as Dennett described it, sphexishness).

Philosopher Fred Keijzer challenges this use of Sphex, citing experiments in which behavioral adaptations are observed after many iterations. Keijzer sees the persistence of the Sphex example in cognitive theory as an indication of its rhetorical usefulness, not its factual accuracy.[9] Of course, the repeated inspection of a disturbed nest may very well be an adaptive behavior, thus diminishing the aptness of Hofstadter's metaphor. As he concludes, "There is no reason for humans to remain stuck in an endless behavioral loop when wasps don’t."[9]


Sphex argentatus
Sphex funerarius with prey

The genus Sphex contains 132 extant species:[10]

Fossil Species[edit]


  1. ^ Pulawski, Wojciech J. (25 April 2021) [2014]. "Family Group Names and Classification: and taxa excluded from Sphecidae sensu lato" (PDF). California Academy of Sciences. Retrieved 14 January 2022.
  2. ^ Fabre, J.H. (1915/2001). The hunting wasps. New York: Dodd, Mead and Company.
  3. ^ Tinbergen, N. (1974). Curious naturalists (2nd Ed). Harmondsworth: Penguin.
  4. ^ Dawkins, Richard; Brockmann, H. Jane (1980). "Do Digger Wasps Commit the Concorde Fallacy?" (PDF). Animal Behaviour. 28 (3): 892–896. doi:10.1016/s0003-3472(80)80149-7. S2CID 54319297. Retrieved 19 July 2015.
  5. ^ Dennett, Daniel (1973). "Mechanism and responsibility". In T. Honderich (Ed.), Essays on freedom of action. London: Routledge.
  6. ^ Dean Wooldridge (1963). The Machinery of the Brain. McGraw-Hill
  7. ^ Hofstadter, Douglas (1985). "On the seeming paradox of mechanizing creativity". In Metamagical themas. Penguin. pp. 526–546.
  8. ^ Dennett, Daniel (1973). "Mechanism and responsibility". In T. Honderich (Ed.), Essays on freedom of action. London: Routledge.
  9. ^ a b Keijzer, Fred. "The Sphex story: How the cognitive sciences kept repeating an old and questionable anecdote" (PDF). Retrieved 19 July 2015.
  10. ^ Pulawski, Wojciech (11 October 2021). "Sphex" (PDF). California Academy of Sciences.

External links[edit]