It's that time of year again, when Tucsonans can see dozens of two-inched metallic midnight-blue or burnt-sienna creatures scampering under our mesquite trees in a methed-out manner, as if perpetually looking for an imaginary missing lighter. They are the Pepsis and Hemipepsis wasps, aka the tarantula hawk, which normally come out of hiding in July, and can be found mid-day just before and after a monsoon rain as they sniff out possible tarantula burrows amongst the mesquite's fallen bean pods.
According to a report by Dawn H. Gouge and Carl Olson of the UA Department of Entomology, the tarantula wasp has the most painful sting in North America, second in the world only to Central and South America’s bullet ant, which earns top ranking on the Schmidt Sting Pain Index. The wasp's sting has been described as something close to sitting in a tub of water and throwing in a toaster oven—blinding and debilitating, leaving the victim a screaming, balled-up hot mess.
After only a few minutes, however, the excruciating pain usually subsides, and the tiny sting resembles that of a fire ant. You pretty much have to purposely pick the wasp up in order to get stung, as they mostly ignore humans. It’s our velvety eight-legged friends that need to beware, for its fate shall be a slow and grisly one as the female tarantula hawk uses the spider as a host for its larvae.
Once stung, the tarantula becomes paralyzed within seconds. The condition will last for the remainder of its life. The wasp may drink the body fluids oozing from the spider’s wounds or from its mouth to replenish nutrients and water she used during the attack.
If the wasp expelled her victim, she will drag it back into its own burrow, now a burial vault, lay a single egg on the spider’s abdomen, then seal the chamber. If the wasp succeeds in stinging a male tarantula on a mating hunt, she will excavate a burrow, drag the paralyzed spider inside, lay her single egg, and seal the chamber.
Once the egg hatches, the tiny grub, initially connected to the spider by the tip of its tail, bends over, attaches its head and begins to suck. It continues sucking until its final moult. It then rips open the spider's abdomen, thrusts its head and part of the thorax inside, and "feeds ravenously," as one entomologist described it. As one might hope, even for a spider, the tarantula at this point is finally dead.
Gene Hall, who is Museum Manager at the UA Entomology Museum's Insect Collection, said of the tarantula hawk, "They are one of the beautiful gentle giants of the desert fauna. We get a lot of inquiries at the UA Entomology Department and try to convince/teach people these wasps are one of the many benefits of living in the desert."
That said, it's probably best if we civilians just let these spazzy little winged critters be, and according to Tucson's Conquistador Pest & Termite, "Tarantula hawks are not aggressive or prone to stinging and most experts recommend that such wasps simply be left alone and preventive measures be taken to keep the wasps from getting into your home or stinging someone." Don't try this at home, folks—if you must, get a professional. As for the crusty neighborhood tweakers, you're on your own.