pepsis wasp

Tarantula Hawks Deliver The Big Sting

Tarantula Hawks, a.k.a., Pepsis Wasps, have the most painful sting of any insect, and they live here in the southwestern desert. There are 15 species in North America, some up to four inches long. The most common species in Arizona appears to be Pepsis formosa, a bluish-black wasp with orange wings. These can get up to two inches long.

TarantulaHawk-large

Just how painful is the sting? Well, on the Schmidt Sting Pain Index, Pepsis wasps (and Bullet Ants) register a 4. Africanized bees, yellow jackets, hornets, and bumble bees register a 2. Dr. Justin Schmidt, an entomologist, recently retired from the U.S. Department of Agriculture’s Tucson Carl Hayden Bee Research Center, allowed himself to be stung by a variety of insects so he could judge the amount of pain. How’s that for a job? Schmidt poetically describes the Pepsis wasp sting as “Blinding, fierce, shockingly electric. A running hair drier has been dropped into your bubble bath.” (He describes the sting of a Bullet ant as pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel.) The pain from a Pepsis wasp sting is said to last only three (very long) minutes.

Although their sting is traumatic, Pepsis wasps are not aggressive and it takes provocation to get one to sting you. So, don’t try to catch one in your bare hands. Only the females sting (but males may fake it), because the stinger is derived from the ovipositor, the egg-laying organ. You can distinguish females from males by the curled antennae of the female.

See the Bug guide for more photos.

Pepsis wasps are most active in the summer although they do try to avoid the hottest part of the day. They are found around flowers or on the ground in search of prey. The adult Pepsis wasps feed on nectar and pollen. It is called a tarantula hawk because it hunts tarantulas (and other large spiders) to use in the wasp’s reproductive cycle. The Pepsis wasp will approach a tarantula and cause the spider to rear its legs, thus exposing its abdomen. The wasp will sting the spider to paralyze it. The wasp will lay an egg on the paralyzed spider and drag it to a hole, bury it, and cover up the hole. When the wasp egg hatches, the larvae eats the flesh of the living tarantula for about 35 days, then spins a cocoon and pupates over the winter. If the wasp egg fails to hatch, the spider can recover.

Most predators avoid the Pepsis wasp. However, roadrunners and bullfrogs are known to tackle them.

Recently my wife, Lonni, saw a very large all-black wasp on our back porch. She claimed it was more than four inches long. For some reason she didn’t get a photo. It might have been a large example of Pepsis mexicana (photo below from http://www.arizonensis.org/sonoran/ ).

PepsisMexicana

By the way, Pepsis formosa is the New Mexico State Insect. (Arizona’s state insect is the two-tailed Swallowtail, a butterfly.)

Videos of Pepsis wasp attacking a tarantula:

Part 1, the attack: http://www.youtube.com/watch?v=5C1wFxEIj8E

Part 2, the kill: http://www.youtube.com/watch?v=D56lxph_WlI

 

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Who’s Afraid of Tarantulas?

The Desert Tarantula, Aphonpelma chalcodes, is the most common tarantula seen in the Tucson area and is one of 30 species found in Arizona. Now, during the monsoon, and into early fall is the time to see them. If you notice holes in your yard about the size of a quarter, it is probably a tarantula hole. You can go out at night with a flashlight and observe the females near their holes. Males are more likely to be seen trekking to find females.

Tarantulas are primitive spiders that evolved almost 350 million years ago and have changed little since. The female Desert Tarantula is usually tan or brownish, while the male is darker, usually with black or dark legs and a reddish abdomen. Females have a large abdomen, bigger than the cephalothorax(upper body), while the males have a small abdomen.

Tarantula female

Tarantula male

Tarantulas dig burrows about 6 inches deep and up to 8 inches laterally, enlarging them as the spider grows. The spiders molt 3- to 6 times a year as they grow, and they can regenerate lost legs upon molting.

Tarantulas are venomous like all spiders, but they are very docile and bite only under extreme provocation. I have picked up many tarantulas and never have been bitten. The venom is usually not harmful to humans. But tarantulas have another defense. Some of the hairs on their abdomen are barbed (urticating hairs) and are very irritating. The tarantula uses its hind legs to flick these hairs at an attacker.

Tarantulas are long lived spiders. They reach sexual maturity at 8- to 12-years old. Females can live up to 25 years, but the males live only one season beyond sexual maturity. Mating takes place in the summer and fall, and the female stores the sperm until the next spring. The female spins a thick layer of silk in her burrow and in concealed places near the burrow to hold up to 300 eggs. Ants are the main predators of the eggs. The spiderlings hatch in about three weeks and stay in the silk cocoon for another 7 weeks while they grow. The survivors disperse and make their own burrows.

When active, tarantulas may set out strands of silk, “trip wires” around their burrow as a signal that a meal is passing by. They don’t like water, and flee if the burrow gets wet. Sometimes a silk cap on the burrow helps keep water out. Tarantulas do need to drink, but can go up to 90 days without water. During the winter, tarantulas become dormant. They plug their holes with silk and soil, and wait for summer.

Pepsis waspAnd now for a gruesome tale. The Pepsis wasp, Pepsis formosa, is a large (up to 2 inches), bluish-black wasp with orange wings. It is also know as the tarantula hawk. It is a parasite on tarantulas and uses the spiders in its reproductive cycle.

The Pepsis wasp will approach a tarantula and cause the spider to rear its legs, thus exposing its abdomen. The wasp will sting the spider to paralyze it. The wasp will lay an egg on the paralyzed spider and drag it to a hole, bury it, and cover up the hole. When the wasp egg hatches, the larvae eats the flesh of the living tarantula for about 35 days, then spins a cocoon and pupates over the winter. If the wasp egg fails to hatch, the spider can recover. These large wasps generally don’t bother humans.

Tarantulas may look scary, but they are very gentle creatures. You need not be aftraid.