Great Golden Digger Wasp: The Other Soil Burrower

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Great Golden Digger Wasps (Sphex ichneumoneus) rival Cicada Killer Wasps (Sphecius speciosus) in size, soil excavating capacity, and heavy lifting.  In fact, research on the foraging capacity of the Golden Digger showed this wasp's heavy lifting capacity exceeded that of the Cicada Killer; it was significantly higher than 15 other hymenopteran heavy lifters.*  Yet, when most people think of big wasp bombers, they think of the Cicada Killer.  That's because Cicada Killers occur in larger numbers and their nesting habits often place them in conflict with people.  Golden Diggers are more secretive; they fly below our radar.

 

Golden Digger Wasps may measure over 1" in length.  These robust wasps are most often found sipping nectar from flowers; adults occupy the lofty position of plant pollinator.  The adults are also effective hunters as recognized by the specific epithet for the species:  ichneumoneus is based on the Greek verb ichneuo meaning "to trace" or "to track."  The wasps focus their tracking attention on orthopteran prey including crickets, katydids, and grasshoppers.

 

Prior to hunting, female Golden Digger Wasps dig burrows by tunneling vertically into the soil, usually to a depth of 4 - 6", and then they excavate lateral brood chambers.  The females prefer to dig in bare, well-drained soil.   Once a female locates her prey, she uses her stinger to deliver a paralyzing shot of venom.  She then airlifts her prize back to her burrow, drags it into a brood chamber, and lays a single egg on surface of her brood-bounty.  The resulting wasp larva consumes the still living orthopteran.

 

Great golden digger wasp

 

*Coelho, J.R. and L.D. Ladage.  1999.  Foraging capacity of the great golden digger wasp Sphex ichneumoneus.  Ecological Entomology, 24: 480–483