Early Miners, part 2

This week we return to the local mining bees.  After I wrote about the ones living in my alley, Evan Sugden told me about a similar aggregation right off the Burke-Gilman Trail, just west of UW campus.  That was interesting, so I went to check it out before the Friday afternoon showing of More than Honey (which is an excellent film, by the way.)

By the time I got there, things were settling down for the day, and there were only a few bees flying.  Even so, I was able to catch a nice bit of drama: a cuckoo bee (that is, a kleptoparasite, probably Nomada spp.) picked the wrong nest to raid, and was rudely evicted by its resident female.  The light was starting to fade, but I was still able to get a decent shot:


I was also able to get a closer look at one of the other females before she disappeared into a nest.


Right away, I can see two things.  It looks like Andrena (which is good, since it’s also acting like Andrena, and that’s what I expected it to be,) and it’s not the same species as the one near my house.

Looking closer, though, things get a bit weird, and nicely illustrate why identifying bees from photographs is a long-term learning experience.  To wit:

  • The structure of the wing pretty much rules out the Colletidae and Halictidae (which is handy, since the default Little (mostly) Black Bee would otherwise be Lasioglossum.)
  • Unfortunately, the bit of wing that’s most useful for telling species of Andrena apart is obscured by a blade of grass.
  • The structure of the head and the distribution of pollen hairs (none under the abdomen, which you can’t see here but I noticed on a flying individual) make Megachilidae unlikely.
  • The ocelli (the three simple eyes on the top of the head) are set unusually far forward for Andrena.
  • There is one feature that is always diagnostic of the Andrenidae: a pair of foveae, or indentations, between the eyes.  I cannot see any.  That doesn’t mean they’re not there – the light is flat, and the base of the area where they might be is obscured by hair – but it’s still disconcerting.

So, my five-minute ID is “probably Andrena, but slightly odd.”

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