Friday, May 16

Cuckoo for California Chrysididae

After a fleeting glimpse of my lifer cuckoo wasp last summer near Sierra Valley, I have spent countless fitful nights longing to gaze at that slender, metallic body once again. One might imagine my sheer delight when, last week, a second grade student on an insect hunt approached with said muse packaged neatly in a small plastic box. Before he could say “Look what I found!” I ripped the container out of his hands and begin preparing my soliloquy on the importance of sharing scientific discoveries. He kindly acquiesced to allowing me to keep the insect temporarily for study.

Upon arriving at the lair of natural history, I pulled the delicate package out of my pocket only to find the beloved critter curled into the familiar insect death pose. “Damn my careless self!” I thought, and stormed off to make a cup of Earl Grey and pontificate my murderous tendencies. After tea and musing, I returned to find the corpse actively crawling about and vigorously shaking its antennae; upon which I promptly fainted on the nearest fainting couch.
It turns out that a universal trait of members of the Chrysidinae sub-family is the ability to conglobulate - curling tightly into a protective ball, tucking the head against the abdomen and essentially playing dead. Not only was the wasp still alive, but its identity had been narrowed down to one of a scant 19 genera.  

Of the 227 chrysidid species in North America, 166 occur in California and around 22 are endemic to the Golden State. With such cuckoo diversity, why then had I not found dozens of these small wasps over the course of my naturalizing career and instead resorted to stealing one from a relatively helpless child? It has to do with their life history and unique habits of reproduction, which also earned them their common name.
Mind raising my kid for me? Also my kid is going to eat yours. Thanks. 
Like their avian namesake, cuckoo wasps are nest parasites. Most genera are parasitic on other Hymenoptera , specifically solitary bees and non-social wasps. The female cuckoo wasp sneaks into the nest of her host and lays an egg, either in a larval cell or directly on the larvae or pupae. Then the cuckoo wasp larvae hatches and eats either the food provided to the host larvae (cleptoparasitism) or the host larvae itself (parasitism). The larval cuckoo wasp then pupates and flies out of the nest unscathed as an adult. As a product of this lifestyle, adult female wasps are most commonly found crawling rapidly along the ground, under plants and on decaying wood where they might encounter a host nest. And that neat conglobulation trick? When you’re entering the nest of a well-armed stinging insect, it helps to have good armor. When rolled into a ball, cuckoo wasps are almost impervious to host attacks and are often carried out of the nest by the defending female - only to stage another siege.

Pits in the exoskeleton provide protection and the brilliant color. 
While I can personally admire this unique take on parental care, I’m afraid many of you may scoff at such a lifestyle and write off cuckoo wasps as worthless freeloading parents. Fortunately, they are also incredibly beautiful – most species in California are a brilliant metallic green or blue. This is due to the diffraction of light upon their multi-layered and heavily pitted exoskeleton, which provides additional protection from stings and bites of host adults. More good news: chrysidid stings have evolved back to their intended use: an egg-laying tube with a reduced poison gland, meaning they have lost the ability to sting.
 
They're stunningly beautiful, have the best parental strategy since Al Bundy, and can't sting.
If after absorbing this fascinating life history you find yourself completely enamored, get outside and start looking on the ground. In California most adult cuckoo wasps are active between May and August, where they can be found nectaring on flowers or crawling about searching for host nests. And if you’re looking for something to write your entomological thesis on (and aren’t we all at heart)? In her definitive tome on the subject, Lynn Kimsey tells us that only 10% of North American chrysidids have an identified host species.

The possibilities are limitless. I recommend using children to find your specimens. 

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