COOL WASPS

My personal life is a mess right now and I don’t really want to write about it (context: it’s 8:08 PM on Sept. 13 as I write this) so I’m gonna go a bit more expository for this essay.

In bug bio today we talked about spiders, then about their natural enemies. The coolest of these are obviously pompilid wasps (a family classification). Each of these gals has to paralyze a spider bigger than itself because larvae need to grow to full size on one spider. That’s a really dangerous feat. The wasp has to fly down to the spider and inject it with a powerful, specialized neurotoxin. In family Pompilidae, the neurotoxin paralyzes the spider while the wasp drags it to its nest. (Mr. Stone said the toxin made the spider docile, but I couldn’t find evidence to support his claims.) Then the wasp lays an egg on the spider and the larva consumes it.

The Pompilid neurotoxins perform a decently simple function: they render the spider immobile. But we see much more fascinating toxins at play in the jewel wasp (Ampulex compressa) and in other cockroach wasps of the family Ampulicidae. These guys are CRAZY. It is completely unbelievable how fascinating they are. 

There’s actually constant new research coming out about jewel wasps. That’s because they are essentially high-pressure neurosurgeons. The female wasp parasitizes cockroaches. The cockroaches are much, much larger than the wasps will ever be, so the wasp can’t drag the cockroach or physically overpower it. Instead, the wasp uses finesse. Before getting a cockroach the female builds a typical wasp nest (hole in the ground). She mates and goes off to find her fortune suitable cockroach prey for her young. Once she gets a cockroach, she stings it twice. Once sting briefly paralyzes the front limbs of the cockroach, essentially a mild form of the spider wasp sting. This allows the female wasp time to maneuver to a specific part of the cockroach’s head. There, she stings one specific portion of the cockroach’s brain. This microscopic region controls, essentially, the will of the cockroach. It’s also called the “escape reflex”. When the escape reflex is disabled, the cockroach can still walk and fly just fine, but it will not resist pain or capture. The most amazing thing about this wasp is the specific chemical and location of the second sting. Researchers (see works cited) even showed that they think the wasp is feeling for the part of the brain necessary to sting, because when it was removed before the sting, the sting took five times as long to complete. It’s puzzling how this very specialized sting could evolve from a more general neurotoxin like the one used by the spider wasp.

Then the female wasp chews off the tips of the cockroach’s antennae and leads it by one of the stumps like it’s a leash. She pulls the cockroach into her nest, lays an egg, and seals the opening. She will make dozens of nests. When the larva in a nest hatches, it burrows into the cockroach’s abdomen and eats its organs one by one, in the order that will keep the cockroach alive the longest. Finally the larva pupates and emerges as an adult like the chestburster from Alien. The life cycle is gory, sure. But it also has so many moving parts that have to go off just right that it's amazing that it works at all!

Research on jewel wasps is very new. There's also a large family, Chrysididae (the cuckoo wasps) with an entire method of coloration that was just figured out in the late 2000s! These wasps’ color varies from blue to green to rainbow. I know. It is awesome. So now you’re thinking “oh wow! They must have so much pigment!” Nope. As far as actual pigment on their exoskeleton, they are basically albino. Instead their six-layered exoskeleton has tiny pores and indentations that are so small that they reflect back certain colors and not others. I’ve only seen one once (they mostly live in the south). It was on a bright, sunny day and I thought I was looking at a sweat bee… until I realized that the blue color was much too bright. These wasps are very, very, very iridescent. The light of the one I saw left a spot in my vision, like looking into the sun, and messed up the white balance on my camera. There’s really nothing like seeing one.

Strangely, these guys are nest parasites. They sneak into other wasps’ nests and lay eggs on the parasitoid prey item. Despite their best attempts, these wasps are often caught red-handed parasitizing a nest. That’s why people are unsure how coloration is an adaptation, since it makes them easy (at least for humans) to see. However, the wasps can wait out the attacks: the pitting of their exoskeleton means the enemy’s blows rarely land. And they can curl, armadillo-like, into an iridescent ball to protect their legs and belly. They might be pushed out of the nest and have to try again, but they will survive. Their peacock colors will live on!

I’ve been interested about these species of parasitoid wasps for a long time. But there are so many cool solitary wasps, and hymenopterans in general. It’s tough to pick only a few to talk about! The order Hymenoptera (sawflies, wasps, ants, and bees) has a wide range of behavior types, from social pollinators like honeybees to solitary parasites like the jewel wasp. Part of the reason I wrote this is that parasitic wasps are not very well-known (certainly not as publicized as “bad guys” like hornets). And they get a bad rap because of their behavior. In fact, they’re what made Darwin atheist: he believed no benevolent God would create a species so evil that it procreates by slowly killing other insects. But these animals also showcase some really, really neat behavior and adaptation to their environment. Also, most are not aggressive at all so if you see one, please don’t run. Instead, snap a picture, identify it, and if it’s something wild you could write a blog post about it.

Informal works cited (sorry the things might be out of order!)

Lukas, David. The Cuckoo Wasp: A Gorgeous Parasite. Bay Nature, July 1, 2012, found at https://baynature.org/article/the-cuckoo-wasp-a-gorgeous-parasite/. 

Gal, Ram, and Frederic Libersat. “A Wasp Manipulates Neuronal Activity in the Sub-Esophageal Ganglion to Decrease the Drive for Walking in Its Cockroach Prey.” Ed. Vladimir Brezina. PLoS ONE 5.4 (2010): e10019. PMC. Web. 13 Sept. 2018. (not in given citation, but doi is doi: 10.1371/journal.pone.0010019)