Anthophora nest aggregation in my yard!
I knew I had some good ground-nesting bee habitat when I found the Halictus rubicundus aggregation in my yard last summer, and I had been excited to see whether they came back this year. But I didn't expect Anthophora! I only see one previous record of them in King County on Discover Life, and only three previous records in King County on iNat. But I spotted one a couple of houses down on Feb 9, then another on Feb 26, both days in the 40s Fahrenheit. Yesterday was the first sunny, 50s-temp day of the year, and it was like an Anthophora explosion! I saw many on a walk within a few-blocks radius of my house. When I got home, I spotted one entering a nest hole in my yard, digging a bit, then pushing dirt out. I waited with my camera, and it slowly, slowly poked its head and then its thorax out, staring at me. There were many others buzzing around, and I spotted >30 nest holes, many of them being actively entered or excavated by Anthophora.
Observations
Photos / Sounds
What
Common Digger Bees (Genus Anthophora)Observer
eebeeDescription
I was astonished to see this bee flying so early in the year! It was 43 degrees F outside according to my weather app. This was on a south-facing hill in bright sun, though, so the local temp might have been slightly higher. I was also surprised to see what looks like an Anthophora over on this side of the mountains; it looks like there are just a few other records in King County. I'm very curious about whether I'm right on the initial ID. The plant it’s on is a cultivated Rhododendron: https://www.inaturalist.org/observations/69327006. It was skittish when I approached, and I took this from >6 ft away with a 300mm lens rather than with a 100mm macro.
Photos / Sounds
What
Common Digger Bees (Genus Anthophora)Observer
eebeeDescription
Seen at the same location as https://www.inaturalist.org/observations/69327007 in the same conditions (mid-40s temp, sunny, south-facing)
Likely the same individual as https://www.inaturalist.org/observations/70224614 but I lost sight of it in between
Photos / Sounds
What
Common Digger Bees (Genus Anthophora)Observer
eebeeDescription
Seen at the same location as https://www.inaturalist.org/observations/69327007 in the same conditions (mid-40s temp, sunny, south-facing)
Likely the same individual as https://www.inaturalist.org/observations/70224613 but I lost sight of it in between
Photos / Sounds
What
Common Digger Bees (Genus Anthophora)Observer
eebeeDescription
This bee was digging energetically in a stump, though I'm 95% sure it's actually a ground-nester in an aggregation a few inches away.
Comments
Nice! I think the males are probably Anthophora pacifica, but not certain. It will probably be clear when females emerge though, since they are quite distinctive (almost entirely black).
Oh, interesting suggestion! I had assumed that the ones in the nest holes would be female--am I incorrect about that?
Typically yes, but there may be some males that are still emerging from their natal nests.
Do you know how long they tend to hang out in their natal nests? And/or whether they dig for females to mate with? This one (https://www.inaturalist.org/observations/70430894) was flying around, and I saw it go into the hole, and then a little after it pushed some dirt out. I also checked that hole again today, and the same or a similar-looking bee with lots of yellow on its face was hanging out inside, looking out from the entrance, like yesterday. (And other yellow-faced bees peering out from nearby holes.) I wish I were better at counting antennal segments.
Here are photos of one in a nearby nest that show the face better. https://www.inaturalist.org/observations/70480530
Also, by evening the nest holes were covered in fresh dirt.
Yes, all of the ones with yellow faces are males. Some other anthophorines are well-known for behaviour in which males will camp out at nests waiting for females to emerge (like the Amegilla in this somewhat dramatized video: https://www.youtube.com/watch?v=KnJ84f9ExXw), but I'm not sure if the same thing happens in whatever species you have.
This is really interesting. I'm jealous of that anthophora aggregation. I am in Clackamas county and I have only seen some bees out as of late. It has been pretty warm here though so I am not sure. :)
I'm sure more bees will come to you soon, @protosmia25!
Today I saw a bee without the bright yellow facial markings in a hole in the aggregation https://www.inaturalist.org/observations/70859247. Possible female?
I also, bizarrely, saw bits of leaf on/in/around the holes, and one getting actively dragged into a hole: https://www.inaturalist.org/observations/70859246
And @trevorsless, thank you very much for that info and for the link to that Amegilla video.
Another without the bright yellow markings on its face: https://www.inaturalist.org/observations/70910936
Discussions about distinguishing these from Habropoda on these observations:
Wing veins and cells: https://www.inaturalist.org/observations/70717602
Links to similar-looking faces: https://www.inaturalist.org/observations/70910936
And one with different-looking hind legs that @protosmia25 and I are suspecting might be female: https://www.inaturalist.org/observations/70979218
That recurrent vein difference is quite clear, yes. Additionally, in Habropoda the marginal cell should be about as long as the distance from its end to the tip of the wing (i.e., imagine copying it and laying them end to end), while in Anthophora the marginal cell is clearly shorter than the distance to the wingtip. But this can sometimes be tricky when the ends of the wings are damaged as often happens in older individuals. And yes, that last observation certainly looks like a female.
These are some really good identification tips, thank you Trevor. I now know a better way to tell the difference between those two similar looking genera. Are there any other ways to tell the two apart?
Those are the main differences I know from Michener, McGinley and Danforth 1994. It's also sometimes described as the submarginal cells bordering about 5half of the marginal cell's bottom edge in Habropoda, but well over half in Anthophora.
For anyone tuning in now, I finally have good pics of a female: https://www.inaturalist.org/observations/71346892
And here are the best pics I have of a male: https://www.inaturalist.org/observations/70717602
Nice photos. :)
Mandibles! https://www.inaturalist.org/observations/71591679
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