Cuckoo Wasp

2011 January 22

We went down to the Stanton Township North Entry Park (“The Breakers”) on June 21, 2010 and Sam found this very, very green insect in the process of drowning in the waves. We brought it home (we didn’t have a jar, so I carried it in my hand the whole way), and once it dried out, it looked none the worse for the experience.

Given that it didn’t sting me the whole way home, it is a good bet that it didn’t have a functional stinger, which narrowed down the possibilities a bit.

At first, I thought it might be one of the several species of metallic-green bees, which are types of “sweat bees”[1]. But looking more closely, there were some definite points making it clear that it was not the same. First off, the wings don’t look like they have “closed cells”, or areas that are completely surrounded by veins.

Second, it wasn’t particularly furry,

And third, the abdomen was kind of dished, so that it could roll up into a ball if it felt threatened.

All those traits (and particularly the ability to roll up) tell me that it was actually not a bee, but rather one of the Cuckoo Wasps, in the family Chrysididae. They are called Cuckoo Wasps because, like the Common Cuckoo in Europe[2], they are “brood parasites”. They look for the nests of various ground-nesting bees, and slip in and lay their eggs in the food stores that the bees are putting aside to feed their own eggs. The wasp eggs hatch first, do away with the bee egg or young larva, and then settle down to eat the stores themselves. So, the Cuckoo Wasp is basically tricking the bee into raising their young for them.

This sort of brood parasitism is probably one of the big driving forces towards social behavior in bees and wasps. If a bee is working alone to build a nest, then there are long periods where the nest is undefended against these sorts of brood parasites. But, if several sisters team up so that one of them is always around to guard the nest, then the chances for a brood parasite to slip in are greatly reduced. And this defending isn’t necessarily combat; some species of ground nesting bees will guard the nest simply by going into the hole and plugging the hole with their head so that things like cuckoo wasps can’t get in. Which is what this bee (or maybe wasp) is evidently doing in these pictures I took on June 19, in the bare soil next to our garage[4]:

The hole was about 4 mm across, and while I was taking pictures the inhabitant backed down a little bit, but kept filling the hole with her head:

It sure looks to me like a cuckoo wasp would have a hard time getting past that.

[1] Sweat bees are small bees that crave salt, and so they are attracted to sweat. They are generally attracted to people who are doing heavy physical labor outdoors in the summer. Like, say, on a dairy farm. When I was a kid, we would have these land on us constantly, particularly when we were out baling hay. They were of no consequence as long as you left them alone, they would just lap up some sweat and then be on their way. But unfortunately, they were easy to confuse with the much-more-numerous biting flies. Swatting a biting fly gets to be second nature pretty quickly, but if you swat a sweat bee she’ll sting you. Luckily, their stings are nothing serious: Justin Schmidt describes them in his Sting Pain Index as “Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm.” My father developed a method for swatting insects where instead of coming straight down with his hand, he would bring it down at an angle so that the swatted insect would be rolled along instead of just being smashed. He claimed that this kept the occasional sweat bee from getting a chance to sting.

[2] It turns out, though, that while many Cuckoo bird species are parasites, the majority of them are not. In particular, only three of the Cuckoo species in North America are brood parasites[3] on other birds, and the two kinds of Cuckoos that we see locally raise their own chicks. Around here, the serious brood parasites are the Brown-Headed Cowbirds.

[3] And lest we start feeling too smug about how we humans are too smart to be brood parasitized, and don’t allow other species to sneak their babies into our homes so that we will raise them along with (or instead of) our own, I would like to say one thing. Cats.

[4] When I first found the hole in the ground with a head plugging it, I thought I’d found a tiger beetle larva. But the mandibles look all wrong for that, so I’m pretty sure it is a bee or a wasp defending her nest from brood parasites.

8 Responses
  1. John Ridley permalink
    January 22, 2011

    Looks pretty much identical to the cuckoo wasp photo that I took back in 2009; even the wing veins look to be in the same pattern, though mine had no interest in hanging around even after a stint in the freezer, so I only got one good photo:

  2. January 22, 2011

    Beautiful shots of the wasp, Tim.

    And I laughed at the “cats” comment – funny and true.

  3. January 23, 2011

    Nice picture, John! I wonder if yours had more blue because it was a different species (if
    BugGuide is any indication, all the North American cuckoo wasps seem to look a lot alike), or if it was just the lighting angle – that iridescent sheen they have seems to vary depending on the quality of the light.

  4. January 23, 2011

    Thanks, Andy. I’m actually a bit surprised that there aren’t more hits on searches for “Cats” and “Brood Parasites”. Well, this will probably be one more than there were before.

  5. Della3 permalink
    January 23, 2011

    Tim, you silly! Of course “cuckolding” is quite common amongst humans! It’s just easier to spot these days, thanks to DNA testing. However, I never understood the derivation of the word until I read your explanation of the cuckoo wasp.

  6. Anne Bingham permalink
    January 23, 2011

    Della3, thank you, thank you, thank you for the etymology of the entomology term! Somehow I missed that in my Chaucer class, but there it is in black and white in the American Heritage Dictionary!

    Tim, I, too, laughed aloud at the cats reference!)

  7. January 28, 2011

    ” And lest we start feeling too smug about how we humans are too smart to be brood parasitized, and don’t allow other species to sneak their babies into our homes so that we will raise them along with (or instead of) our own, I would like to say one thing. Cats.”

    Oh please. Cats don’t kill off the baby and they drink only a modest amount of the milk. And would it kill you to open a can of tuna once in a while?

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