Nights of the Living Dead… Further Horrors of the Insect World

Common Name: The Tarantula Hawk

A.K.A.: Genera Pepsis and Hemipepsis

Vital Stats:

• The two genera make up Tribe Pepsini in Family Pompilidae
• Grow up to 5cm (2”) long
• Stingers are up to 7mm (1/3”) long
• Quite long lived for wasps, with lifespans of more than a year
• Adults feed primarily on milkweed nectar

Found: Across much of the tropics and southern hemisphere

It Does What?!

Happy Halloween, readers! Today’s the day when we’re surrounded by images of zombies, witches, ghosts, and spiders- all creatures meant to scare us on some level. Of course, only one of these things is real. And spiders truly are a scary thing for many people. For all you arachnophobes out there who are feeling vaguely uncomfortable about the preponderance of fake spiders out there today, did you ever wonder what the spiders fear? What keeps tarantulas, the biggest, scariest arachnids of them all, awake at night? Tarantula hawks, that’s what. If spiders had Halloween, this is what they would dress up as.

Like any good mother, the female tarantula hawk wants to ensure that her baby has all the food it requires to grow up into a healthy adult wasp. Rather than bag a large piece of prey and have it spoil by the time her egg hatches, she has developed an ingenious system of keeping meat fresh.

Spying a tarantula from the air, she will attack, injecting the spider with her venom as it struggles to bite her. A particularly hard and slippery exoskeleton renders this counterattack ineffective; the fangs simply slip off her. Before long, the tarantula has succumbed to her venom and is alive, but completely paralysed. Once the prey has been neutralised, she sets out over land, dragging the spider up to 100m (quite a long way, considering the scale involved) back to the site of a burrow she has dug out. Here, our mom-to-be lays a single egg on the helpless spider’s abdomen, then proceeds to immure it in the burrow.

But this is only the beginning of the horror for the paralysed spider. Soon after, the egg hatches, and the hungry larva tunnels directly into the spider’s flesh, eating as it goes. The larva instinctively knows to avoid the tarantula’s vital organs as it eats, thereby keeping the prey alive for as long as possible. After several weeks of chowing down, the larva finishes off the job and emerges from the spider’s body, having now matured into a wasp. It then simply unseals the burrow and flies away, leaving the late tarantula in its ready-made grave.

Wondering what happens when a person gets stung by one of these? It’s an interesting question, because the answer is both “a lot” and “not much”. You see, the paralytic agent in the venom only works on invertebrates, and won’t actually do any real damage to human tissue. Before you go trying to catch one, though, know that, in terms of immediate reaction, tarantula hawks are considered to have the single most painful insect sting in the world. It’s best described by an entomologist who has actually experienced such a sting:

“Advice I have given in speaking engagements was to ‘lay down and scream’. The reasoning being that the pain is so debilitating and excruciating that the victim is at risk of further injury by tripping in a hole or over an object in the path and falling onto a cactus or into a barbed wire fence. Such is the pain, that few, if any, can maintain normal coordination or cognitive control to prevent accidental injury. Screaming is a satisfying expression that helps reduce attention to the pain of the sting itself.” [Schmidt 2004]

In short… don’t touch these.

A few words now on just how frighteningly well-adapted this wasp is. Not only is it covered in armour and full of incredibly painful venom, but at roughly the size of your little finger, it’s one of the largest wasps out there, and more of a fight than most insectivores want to deal with. It is essentially without predators. And lest any potential enemies forget why they’re not touching it, the tarantula hawk has both a distinct colour and a characteristic odour, meant to remind aggressors of the pain associated with any previous run-ins. Researchers have described tarantula hawks as being “among the best defended animals on earth” [Schmidt 2004]. And because success always spawns imitation, there are now several other creatures mimicking the appearance of the female tarantula hawk as a form of protection, including the more-or-less defenceless males of the same species.

So the next time you shudder at the thought of a tarantula stalking you in the wild, stop and remember what might be stalking it.

[Fun Fact: Despite its phenomenal pain-inducing qualities, tarantula hawk venom is only about 5% as lethal as honeybee venom, based on studies by people who inject white mice with horrible things for a living.]

Says Who?

• Alcock & Kemp (2006) Ethology 112: 691-698
• Kurczewski (2010) Northeastern Naturalist 17(1): 115-124
• Schmidt (2004) Journal of the Kansas Entomological Society 77(4): 402-413
• Schoeters et al. (1997) Canadian Journal of Zoology 75: 1014-1019