Because summertime is wasp time, this column features the second remarkable wasp in a row. Females of the Leucospis genus have a convoluted and somewhat shocking egg-laying system, so fasten your seatbelt.
Leucospids are part of the Chalcidoidea wasp super-family. Chalcid wasp larvae are parasites of other insect’s larvae and the adults have cool physical traits like spurs on their swollen back legs, and a wheelbarrow-like stance. Many Chalcids are just a few millimeters long, so Leucospids are the giants of the bunch at about a half inch.
Leucospids do a great job at mimicking stinging wasps. They dress in the traditional yellow and black stripes, and their wings fold longitudinally, like the “hotdog” fold of the classroom, and are held in a V, as stinging wasps do. Where the costume fails is in the bulb-shaped abdomen.
That rounded abdomen is where things get especially weird for the females. See the slim, stick-like apparatus slung over its back? That’s an ovipositor, or egg-layer. When I first learned what it was, I tried to picture how the female would uncurl its back end to use the tiny tube to lay eggs. I thought it must be quite a trick to swing that organ around 180 degrees. It turns out the story is more bizarre than that—the ovipositor you see is a covering for the actual egg layer.
Oregon Leucospis affinis prefer to feed their young on mason bee larvae, which grow up in natural cavities, generally in wood. Females locate a nest by tapping with their antennae (how do they sense a nest? no one knows). Then, as you can see in the video linked below, they unhinge their abdomen, splitting it wide open, which exposes a mere membrane that covers their inner organs. They then release the super-thin, flexible ovipositor from its sheath, like a whip. The outer covering remains in place over the back, pointing skyward, and the wasp uses its raised hind end like the counterweights of an oil well pump to drill the ovipositor deep into the bee nest. Slow down the video from 24 to 32 seconds to get your brain around how they do this. It is wild.
Leucospis females drill through very dense materials, and it can take 10 minutes to get the job done. People who’ve watched the phenomenon are amazed the wasp would make itself so vulnerable for so long, but the technique obviously works, because new generations show up every year.
Stay curious!
Sources:
Paul Westrich’s mind-bending Leucsopis ovipositing video: https://vimeo.com/137164873. Accessed 8/5/21.
Summary of a species in the Leucospidae family from Cornell: http://insectsofcornellgrele.weebly.com. Accessed 8/5/21.
