Last week I saw a large tarantula hawk wasp (Pepsis sp) that had fallen into the wildlife water bucket. Olympic swimmers they are not. It was still alive so I scooped it out and set it onto the ground, where it stumbled around a bit trying to regain its footing after its nautical experience. I went back inside.

A short while later, I saw a desert spiny lizard (Sceloporus magister) facing down the wasp, which had been backed into a corner underneath a claret cup hedgehog cactus by the pursuing reptile. I grabbed the camera and stepped outside to try to get some shots of the thrilling action, or at least any that might yet happen, but managed to snap only a few images before the suspicious lizard darted away.

How would this have turned out had I not interrupted the scene, which I tried not to do by staying a good 15 feet away and mostly hiding behind the corner of the house? I know desert spiny lizards are quite skittish about people since they seldom hang around once I appear, even though I’m not a danger. I can’t imagine that the wasp wouldn’t have stung the lizard harshly in a battle, and it’s hard to imagine that a reptile weighing only 2 ounces at most could easily walk away unscathed from one of the insect world’s most potent venomous stings. Tarantula hawks have very few natural predators simply because of their exceptionally painful stings, used to paralyze spiders used for food, and virtually nothing will attempt to eat them save for roadrunners, from what I read online. Was the lizard stupid? Or simply inexperienced?

Then again, these two species have been cohabiting in the southwestern deserts for untold eons, and you’d think that avoidance or predation instincts in the lizard towards this particular prey item would be built into the behavioral coding by now. Maybe desert spiny lizards are immune to tarantula hawk venom? Maybe the temptation of a big meal in a dry spring was overriding caution? I don’t know. Whatever the case might be, I didn’t get to see an epic battle, because my role as the observer interrupted the dynamic between these two critters. The lizard incorrectly saw me as the threat and not the wasp, which might or might not have been one too.

Guess I’ll never know if I saved the wasp from the lizard, or if I saved the lizard from the wasp….

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Looking online a bit farther, there are few indications that lizards or anything else ever eat large female tarantula hawk wasps. It’s hypothesized that Pepsis (and the related genus Hemipepsis) wasps have evolved exceptionally painful stings in part because they have to spend so much time foraging out in the open desert, looking for hidden spider burrows. Tarantulas are mostly nocturnal, while the wasps are diurnal, and this mismatch of activity leaves wasps to be quite visible. Tarantulas are hidden underground most of the time for most days, and for most months of the year, and are widely dispersed and comparatively hard to find, so the female wasps must spend a large amount of time hunting for them. This exposes them to numerous potential predators in broad daylight. By evolving one of the wickedest stings in the insect kingdom, however, they deter nearly all predators from even making the attempt.

I am also guessing that there are two major classes of chemicals in Pepsis wasp stings: The paralytic type that acts quickly upon a tarantula’s nervous system to disable it and turn it into hapless food for the worst horror movie scenario imaginable; and the pain-inducing type that acts upon the nervous systems of everything else that might see a large black and orange wasp as a snacky treat. While the wasp’s sting is notably awful to humans, it is also not really generally dangerous from a survival standpoint. The worst pain lasts a few minutes and while I am sure that the memory lasts a lifetime (like it’s supposed to) the actual physical effects are generally not lasting.

Of course there is some chance that certain people might be allergic to the venom of these wasps, but overall, despite the fearsome pain they produce they are not really known to hospitalize people, much less kill them. Honeybees have less painful stings but many more people are allergic to them and can die from them. The word is still out on whether lizards have to go to Lizard Urgent Care clinics. Tarantulas go to the morgue.

For more reading, visit this excellent blog post on tarantula hawk evolutionary behavior in the context of why their behaviors and sting self-defenses are so interesting:

https://undark.org/2016/05/18/tarantula-hawk-wasp-sting-pain/