Tarantula Hawk Wasp

• Its sting occupies the top level of the Schmidt pain scale: it is described as a blinding electric shock lasting some five minutes, and the entomologists' practical advice is simply to lie down and scream.
• Even so it is not aggressive and almost never stings people unless handled.
• It is the official state insect of New Mexico, chosen by a vote of schoolchildren in 1989.
• Its sting is the second most painful in the insect world: it scores 4.0 on the Schmidt sting pain index, behind only the bullet ant.
• Yet the venom is barely toxic. The lethal dose measured in mice is extremely high, so its defensive value rests solely on pain, not damage. Schmidt described it as a blinding electric shock lasting about five minutes.
• Only the females sting, because they are the only ones that hunt.
• It hunts tarantulas far larger than itself. It locates the burrow, draws the spider out, paralyses it with a precise sting and drags it to a nest where it lays a single egg on it. The larva devours it alive, leaving the vital organs for last.
• The tarantulas do not win: specialists note that not a single documented case is known of the spider killing the wasp.
• That extreme pain has generated a whole mimicry complex: other wasps in the group share its warning coloration (Müllerian mimicry) and several harmless insects imitate it (Batesian mimicry).
• It is the official state insect of New Mexico, chosen in 1989 by a vote of schoolchildren.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Deserts and arid scrub of southern North America and South America

Sexual maturity

Only the females hunt and sting: the stinger is a modified ovipositor and the males have none. Both sexes form mixed aggregations on the vegetation during the midday heat and at night

Gestation / incubation

The egg hatches after 3-4 days and the larva consumes the tarantula alive over several weeks, leaving the vital organs for last; it kills her in the fifth instar, spins a silk cocoon and pupates. Full development from egg to adult requires about 41 days at 30 °C and 70 % relative humidity

Litter / clutch size

A single egg per tarantula, laid on the abdomen of the paralysed spider; the female drags her to a burrow, often the spider's own, and seals the entrance

Sources consulted: Schmidt (2004 y 2016), The Sting of the Wild · Natural History Museum de Londres · Encyclopaedia Britannica · Vardy (2000) · Arizona-Sonora Desert Museum, ficha Pepsis Wasp · Britannica, ficha Tarantula hawk · guia de identificacion del genero Pepsis · Ficha de especie de Pepsis grossa · guia de identificacion de Pepsis · Ficha de especie de Pepsis grossa (Backyard Nature) · Arizona-Sonora Desert Museum

Best time: The females hunt on foot, with quivering wings and vibrating antennae, mainly in the first and last hours of the day to avoid overheating; the adults take nectar, especially from milkweeds