tarantula hawk

tarantula hawk, (genus Pepsis), genus of about 130 species of spider wasps that paralyze spiders to feed their larval young. Tarantula hawks are found on every continent except Europe and Antarctica and are especially common in the southwestern United States through Central America. The tarantula hawk’s sting is said to be one of the most painful insect stings in the world, second only to that of the bullet ant (Paraponera clavata).

Physical description

Tarantula hawks are some of the largest members of the spider wasp family. The largest species, Pepsis heros, can measure as long as 11 cm (about 4 inches), while more common species such as P. grossa and P. thisbe reach about 5 cm (2 inches) in length. Their slender bodies are generally steel blue in color and are often somewhat iridescent in shades of blue-black, blue-green, or blue-violet. Most have orange, amber, or blue-black wings with distinctive venation. Their coloring serves as a warning to potential predators. Males and females are easily distinguished as the females have curled antennae while those of the males are straight. Additionally, only the females have a stinger, which is curved and can be as long as 7 mm (0.25 inch). It can be difficult to tell apart the different species. The related spider wasps of the genera Hemipepsis and Entypus are similar in appearance.

Natural history

Tarantula hawks are generally rather docile, and their adult diet consists mainly of nectar and pollen from flowers. However, their name derives from their discomfiting reproductive behavior, in which they capture live spiders—often many times their size—to feed to their young. Tarantula hawks are solitary wasps, meaning each female provisions her own nest without the support of a colony. After mating, a female tarantula hawk begins to hunt for large spiders, such as trap-door spiders or tarantulas. The wasp must usually lure an unfortunate spider out of its burrow but will also prey on vulnerable male spiders who venture out to look for a mate. If she finds a spider in its burrow, the wasp mimics captured prey by tapping her feet on the webbing outside the spider’s lair to entice it to exit. Once she has her victim in the open, the wasp uses her stinger to inject a potent venom into the nerve ganglia on the underside of the spider’s thorax, which paralyzes the spider but does not kill it. The wasp then drags the hapless arachnid back into its own burrow or to a burrow she has prepared, where she deposits a single egg on the spider’s body and seals the burrow entrance with debris.

The egg hatches in three to four days, and the wasp larva immediately begins to feed on the immobile but still-living spider by sucking hemolymph, the invertebrate equivalent of blood and lymph, from its body. The larva undergoes five growth stages and progressively consumes more of the spider’s body. During the fifth stage, the young wasp finally eats the spider’s vital organs, killing the arachnid. The immature insect then forms a cocoon and emerges as an adult tarantula hawk two or three weeks later.

Sting

Although the wasps are not aggressive, the females may sting when provoked. The sting of the tarantula hawk is known to be incredibly painful and is rated 4.0 on the Schmidt sting pain index, developed by American chemist and entomologist Justin O. Schmidt to categorize the stings of ants, bees, and wasps. Schmidt, who used himself as a test subject for his index, described the pain of a tarantula hawk sting as “Blinding, fierce, shockingly electric. A running hair dryer has just been dropped in your bubble bath. A bolt out of the heavens. Lie down and scream.” He has also described it as “instantaneous, electrifying, and totally debilitating.” Fortunately, the pain does not last long—only about five minutes—and the venom generally does not harm humans. Roadrunners are one of the tarantula hawk’s only predators known to brave the sting.