O.K., so I was wrong. It happens every once in a great while – like solar eclipses and comets that arrive only a few times in a lifetime. O.K., so I am wrong about the infrequency of my wrongness, but I rarely mistakes (insert wink icon here and add the word “make”). Anyway, in the presence of small quick flying metallic green hymenopterans (bees and wasps) I generally resort to calling them cuckoo wasps. These emerald iridescent creatures get their name from their habit of parasitizing other wasps, just like European cuckoos which lay their eggs in other bird’s nests. They are electric green and fairly common, so most of the time my cuckoo wasps turn out to be just that. In a recent episode of hymenopteran naming, however, my cuckoo wasp label turned out to be, well, cuckoo.
During the initial stages of an archaeological dig, which I conduct as part of the interpretive program at the museum, we started scraping the soil to begin the day’s dig. A few electric green insects were exposed a few inches down and they took wing soon after being revealed. “Cuckoo wasps, “ I confidently proclaimed. A few more came to light after a few more scrapes and again I identified them as cuckoo wasps to the volunteer archaeologists around the pit, although I was beginning to wonder what was going on. You usually don’t see a whole bunch of cuckoo wasps together any more than you see a flock of cuckoo birds. There was an outside chance that this was an unusual example. The third bout of scraping uncovered something very unusual indeed. This find proved to be the one which allowed me to de-cuckoo my green insects and give them the proper name they deserved.
There in the soil appeared something which appeared to be a perforated metal plate (see here a camera phone image of the find). In fact, one of the diggers pointed out that it looked just like an A.C. Delco Oil Filter – a PF3361 to be exact. Now this archaeological site is an old house site that dates Ca. 1800-1860, so one wouldn’t expect to find an oil filter there! Whatever it was, it was very hard but didn’t feel like metal. It felt more like hard cardboard. Just about the time I was about to proclaim it an early paper version of an oil filter, several of those green “cuckoo wasps” poked their heads out of the “holes” (see detail here). Since cuckoo wasps don’t nest in colonies, these things had to be something else. In other words, I was wrong.
In the final diagnosis, this structure turned out to be a grouping of Halictid Bees. I was able to arrive at the correct solution after hitting the books and looking at a few internet references. Even though the general appearance helps, the final call came only after examining the wing venation – the details of which I will spare you. These metallic green bees are sometimes referred to as sweat bees because of their alleged habit of licking up perspiration. In detail (see below and beginning photo) they are stunning examples of the bee clan. Most of the exposed bees were newly emerged adults fresh from the pupal stage.
There remained one more hurtle to overcome in this case. Halictid Bees are solitary bees which dig burrows in which to raise their young. They are not colonial. So, why the hive-like look? In this case what we have is merely a collection of burrows. The individual bees do not work together and, although they may talk over the fence every now and then, they do not barrow cups of sugar. Beyond the even pattern of holes, the individual burrows take their own divergent routes. This type of Halictid Bee is actually taking some evolutionary steps back toward colonialism (and no, I did not make that fact up).
Now, we have all the answers in one place and the world can remain turning. I could only imagine the consequences of discovering that our early Michigan settlers used AC Delco oil filters and that cuckoo wasps run the earth.
Unfortunately, it was too late to tell all this to my volunteers. I’ll have to fess up next time I see them. Come to think of it, our dig season is over, so I won’t see them until next year. Gee, I hope I don’t forget to bring the subject up.