Caterpillar mummy wasp (Genus Aleiodes)
I probably should have saved this week’s crawly for Halloween week, but what the heck, let’s make it a spooky valentine instead. Meet the caterpillar mummy wasp (Genus Aleiodes).
It’s surprising I couldn’t ID this bitty pretty to species, those blue eyes sure POP and are fairly unique among mummy wasps. However, mummy wasps are braconid wasps (Family Braconidae) and with 1700 species in North America and 120,000 species worldwide – it can be tricky to find the time to ID them all to the more specific levels, so the reference materials aren’t always available.
Luckily (for us, very much unlucky for caterpillars) the unique lifestyle of all our local mummy wasps is quite similar so we can still get to know this blue-eyed lady.
Mummy wasps, like all braconids, are parasitoid wasps. They lay their eggs on or near the host critter and the baby wasps dine on the unfortunate host. They then spin a cocoon on the what’s left of the outside of the host and soon hatch out into winged waspy adults.
Unlike most of their 1700 cousins, mummy wasps earned their moniker because they go through their entire juvenile life cycle inside their caterpillar hosts. They hollow out the pillar leaving them picture perfect though dried – ergo “mummy” – on the outside while they are holed up safe on the inside.
The wasp larvae even attach the pillar mummy to plant matter with silken thread to maximize the illusion that the pillar is just hanging out. Of course they do risk being snatched up by a hungry bird, but mummy wasps have been at this for eons – there are many samples of mummy wasps trapped in ancient amber – so clearly their husky camo works more often than not. If it ain’t broke and all that.
In addition to having a cool, spooky name and unique life cycle, mummy wasps are “Capital B” beneficial wasps especially in forested areas, like our own backyards.
Mummy wasps parasitize many caterpillar species. Hosts include several important forest pests, such as the spongy moth, eastern tent caterpillar, forest tent caterpillar, fall webworm, tussock moths, dagger moths, prominents, cutworms and loopers.
Most of these diminutive (about one-quarter of an inch in length) mummy wasps lay one egg per caterpillar, so the little larvae have the equivalent of studio apartments. When they morph to adult form, they chew a single small opening in the pillar mummy to exit.
Then there’s the stigmata mummy wasp (Aleiodes stigmator) who enjoy a more communal childhood. The mum stigmata wasp goes for larger species of caterpillar, she needs to because she will lay up to 45 eggs in a single pillar.
The “stigmata” moniker comes from the multiple exit holes left in the mummified caterpillar as the gregarious young emerge.
While the life cycle of mummy wasps is quite ooky and spooky, it’s also quite fabulous. Parasitoid wasps play a vital role in keeping ecosystems healthy. They are super diverse and usually highly specialized for specific hosts, many of which are herbivores.
Without parasitoid wasps, our beloved flowers, plants and trees would be overrun with herbivorous and other pest arthropods.