Wednesday, August 18, 2010

Wasp Wednesday: Chlorion aerarium

I think the first time I saw specimens of the Steel Blue Cricket Hunter, Chlorion aerarium, was in the collection at Oregon State University in about 1979. I remember being somewhat surprised that the species even occurred in that state, but here it was, all impressive in metallic teal. The specimens dated back at least a couple of decades or so, but I hoped I could eventually find specimens myself.

This magnificent wasp is frequently confused with the Blue Mud Dauber which I wrote about last week. Both are in the family Sphecidae, and indeed they can sometimes be difficult to tell apart in the field, especially the males. Chlorion aerarium is generally a significantly larger wasp, much brighter in color (though a deep metallic violet blue in much of eastern North America), and less hairy than the Blue Mud Dauber. The antennae of Chlorion originate lower on the face, and the mandible has a single tooth (the mandible of Chalybion is simple). Obviously, one can’t easily examine live specimens at close range to note those more subtle characters. Not without getting painfully stung, anyway.

The Steel Blue Cricket Hunter is so named because the solitary females hunt crickets of the family Gryllidae as prey. Watch for the females scouring the ground and peering into nooks and crannies in search of crickets. Once she locates one, she stings it into weak paralysis and flies it or carries it to a simple burrow she excavated previously. She sometimes chooses to dig her own burrow from inside the entrance of a cicada killer burrow, oddly enough.

The burrow may terminate in more than one cell (multicellular burrows may even be the norm). The female places several crickets in each cell, closing the cell with a plug of soil between forays. A single egg is laid on one of the victims. The larva that hatches then consumes the cache of crickets.

Both genders fuel their frenetic activity mostly on fermenting plant sap oozing from wounded shrubs. That is certainly the case here in Arizona where they can congregate by the dozens on oozing Desert Broom plants (Baccharis sarothroides). All of my images here are from such circumstances. Only rarely does this wasp visit flowers for nectar.

While I have found this species to be common and widespread over most of the United States and adjacent southern Canada, I still remember well my first encounters with them back in The Dalles, Oregon, in the Columbia River Gorge. I actually took a Greyhound bus from Portland to explore the sandy high desert habitat there and found many species of wasps. A railroad bed ran near the river, among tall grasses, mountain ash trees, and an overabundance of poison oak. It was in this area that I found many male Chlorion flitting among the poison oak.

Emerging from the tall grass at the very edge of the railroad tracks I saw a female on the ground. She shined like a living jewel, her body in vivid metallic blue with shimmering blue and violet wings that flicked nervously as she searched for prey.

The following autumn at Oregon State I took my specimens to my mentor, the late Dr. George Ferguson, eagerly awaiting his expert opinion. He initially concluded they were merely Blue Mud Daubers. I confessed I was disappointed, having thought they were Chlorion. Dr. Ferguson then put one under his microscope and said “By golly, you’re right! They’re awful small, though.” What music to my ears to be validated by someone I greatly admire to this day.

Common as a given insect might be, there is still a thrill in discovering it for oneself, and if this blog accomplishes nothing else than to nudge a reader into the field in search of his or her own Moby Dick, then I cannot ask for more. Go, find the “bug” of your own dreams, and tell everyone else about it, too.

22 comments:

  1. I have a paper wasp I believe eating my cabbage worms for me.Got a few shots, but they are a good friend now.

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  2. Thank you so much for this post! You helped me identify a female that I found flying a cricket around town. :)

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  3. i think i may have one or more living underneath my garage. glad i found this site telling me what it is...

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  4. I have one of these living in my backyard and it does not seem aggressive, but are they dangerous? Have they been known to bite or sting people and how painful is the sting?

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    1. Solitary wasps in general are loathe to sting unless you physically grab one. I imagine it would be painful, but the venom only weakly paralyzes its cricket victims, so....

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  5. I found it!
    I was in my driveway this morning when I noticed a large bug on my neighbors side wall. It wondered around in short, erratic bursts. When I went to see it turned out to be a large wasp, or hornet, that was chasing one of my sweet crickets. Black winged with greenish iridescent lower body. I had seen one 26 years ago (pinched between the fingers of my then 6 month old daughter) and have always wondered how dangerous that event had been.
    Todays visitor looked more "teal" while I remember the other as being smaller, less tapered at the waist, and more green. Are these two the same species only male and female?
    (Going "organic" in my yard has been an adventure in insects! Paper wasps eating caterpillars even. )
    Barbara

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    1. This species varies greatly in color from bright "teal" as you say, to deep violet. Gender has little to do with it, but the darker ones are found farther north and east.

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  6. We just moved into a house that has MANY of these flying by the back door in the evening. The backyard is very overgrown (I'm working on it) but is there anything else I can do to get rid of these?

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    1. I strongly suspect it is not this species you are seeing, but instead males of the Blue Mud Dauber, Chalybion californicum. Males of that species gather in "bachelor parties" to spend the night in a sheltered spot. Male wasps do not sting. Lastly, I do not give out pest control advice on this blog.

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  7. One lives under my apartment front door it greets me every morning when I step out for a cigarette it scares the crap out of my friends lol

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  8. I have many living in my garage in many old yellow jacket nests. When I first saw them last year, I was curious as they are really pretty and were not aggressive like the previous residents. After I researched what they were, I let them reside in my cricket filled garage and they have resided there ever since, until recently. I noticed that I haven't seen my friends much lately and I can only think that they moved out as they have harvested all the crickets as I do not see them around either.

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    1. I think it is more likely that you are describing the Blue Mud Dauber, Chalybion californicum. They look nearly identical, but the Blue Mud Dauber would be a much more likely garage inhabitant.

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  9. I think I may have seen one earlier today but I'm not sure,but I live in Michigan and a very dark blue wasp was flying near me before I went out for a run, as I am scared of wasps for past expierences I kinda jumped around, I didn't get stung though, but I was wondering if it was the same wasp

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    1. Could have been, but the Blue Mud Dauber, Chalybion californicum, is nearly identical, and would be more common up that far north. Both wasps are solitary and your risk of being stung is minuscule.

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  10. Please help me identify this little guy. Looks like the cricket hunter but has a long stinger like thing.

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    1. Sounds like maybe a female Sirex sp. horntail wasp. The "stinger" would be her egg-laying organ (ovipositor).

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  11. Hello Eric,
    I live in Saudi Arabia, Riyadh City.
    I found one of these in my OFFICE 6 - 8 months back... I let em be, because it didn't seem to be harmful. It would disappear then reappear after weeks or so...
    Now after So many months, I saw 2 of em, and that got me worried if they started nesting... so I hunted one down for study purpose, as I was unaware of this bug type, so I did some research about it and ended up here.
    As iv'e read so far, They don't exist in this part of the world, so I wonder how they ended up here.
    The one I got is pretty much the same as the one you posted on TOP in your article, just that mine ones wings are more transparent with little translucency...

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    1. There are *other* species of Chlorion in other parts of the world, plus many other genera of Sphecidae that closely resemble Chlorion.

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  12. I got stung by one! And OMG! I've been stung before by the average bee and Hornet, but these buggers pack a huge punch! I was close to Lake Erie in a town named Port Burwell. Laying on a blanket outside enjoying the sun. Well I felt a sting. Swept it away with my hand and it was a Steel Blue Cricket Hunter! Well it started out as a bright red mark about the size of a softball. Then burning like gasoline had been poured on area and lighted on fire. Then dizziness, nausea, and sweat started. Had to lay down. It finally passed and I felt a bit better. But where I got stung was RED! Then in a few days it turned BLACK. And I mean BLACK!! Size of a softball and very tender to the touch. It scared me! I had never seen these before. But I now stay far away from them! Not a fun ride! I healed in about 4 to 5 weeks or more. Then the BLACK started to fade away to a normal looking bruise. Nasty!

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    1. I'm very sorry you had this kind of reaction, Bonnie! Our own immune system reaction is often responsible for out-of-proportion agony and severe symptoms. Just be glad you aren't a cricket! Glad you lived to tell, I know allergic reactions are a serious matter.

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  13. I have a wounded tree oozing sap outside my window with a lot, around 20, of what I believe to be these wasps. They are about 2 inches. I live in south eastern Arizona. Does it seem like these wasps or the blue mud daubers? Either was they are beautiful and creeping me out. I have a picture but couldn't see how to attach it.

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    1. Hi, Kathy. This species is very common where you live. In fact, that is where I got these pictures (Arizona). Baccharis (Desert Broom) often oozes sap and that is where I usually see the wasps, plus beetles, flies, butterflies....

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