Digger wasp

Digger wasps
Sphex pensylvanicus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Sphecidae
Subfamily:	Sphecinae
Tribe:	Sphecini
Genus:	Sphex Linnaeus, 1758
species
More than 130; see text

Wasps of the genus Sphex (commonly known as digger wasps) are cosmopolitan predators of the family Sphecidae that sting and paralyze prey insects. There are over 130 known digger wasp 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. When the wasp larvae hatch, they feed on the paralyzed insects.

The well-known species 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.

Uses in philosophy

Some writers in the philosophy of mind, most notably Daniel Dennett, have cited the behavior of this animal for their arguments about human and animal free will.

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 again and again, with the Sphex never seeming to notice what is going on, never able to escape from its programmed sequence of behaviors. Dennett's argument quotes an account of Sphex behavior from Dean Wooldridge's Machinery of the Brain (1963). Douglas Hofstadter and Daniel Dennett 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 Hofstadter described it, sphexishness).

In addition to this seemingly instinctive and programmed behavior, the Sphex has been shown, as in some Jean Henri Fabre studies, 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 and other behavior of Sphex were studied by the ethologist Niko Tinbergen, as explained and demonstrated by Richard Dawkins in the 1991 Royal Institution Christmas Lectures, Growing Up in the Universe.

Species

Great Golden Digger (Sphex ichneumoneus)

Sphex argentatus

Sphex funerarius with prey

The genus Sphex contains over 100 species:^[1]

References

External links

• Great golden digger wasp Sphex ichneumoneus - large format diagnostic photographs, wasp with katydid prey
• Online Identification Guide to eastern North American Sphex