This bee was initially found here on flowers of water speedwell (Veronica anagallis-aquatica). It then flew onto a leaf of another plant, where I took further photos.

I keyed this to genus Hylaeus using Stephen, Bohart, & Torchio(1) (I could barely make out 2 submarginal cells from one of my images). I then checked that putative genus against images on BugGuide, and it seemed good.

Next I searched for literature on Hylaeus and found a number of papers by Snelling (see bottom of info page). I couldn't make much headway from my photos using the three Snelling references I searched out online, though I think I can eliminate the introduced species H. punctata, since Snelling (1983) mentions males consistently had mandibles without pale marks (see 10 lines from the bottom of pg. 14 here). My specimen here has mandibles with a large yellow stripe.

Finally, I went to the Discover Life web site and using the interactive "check box" key for Hylaeus there, I entered various characters that I could see in my images (listed below, for those interested) and eventually got to a single result: H. modestus. (I wish I could link to the resulting Discover Life web page with the final character choices I entered, but the URL doesn't update on that page after I enter data and click "Search"...so when I copied the final URL into my post here and tested it, rather than reproducing a replica of the web page I filled in, it opens a standard entry page for the entire Discover Life site.) I *was* able to get a working link to a map at an intermediate step in the process, where I had narrowed it down to three candidate species...see here. And here's the Discover Life web page for Hylaeus modestus.

Finally, here's a list of the characters whose checkboxes I clicked on the interactive key for Hylaeus on the Discover Life web site (unfortunately I can't figure out the URL to link to in order to send folks to that page).

    3. (Head) length of eye vs the greatest length of the face = Eye is GREATER than 75% of face length;
    5. (Head) mandibles, color = YELLOW, at least in part;
    9. (Head) labrum, color = black;
    13. (Head) pale facial markings = Largely remaining in contact with the eye margin, IF leaving eye margin then NOT curving towards antennal bases ;
    15. (Abdomen) T1, color = All black or black-brown;
    16. (Head) antennae, greatest width of scape vs greatest width of flagella = NORMAL, not expanded, less than or approximately equal in width;
    17. (Head) antennae, scape, overall color = All DARK;
    18. (Thorax) pronotal collar, color = With a pair of ivory or yellow markings;
    19. (Thorax) scutum, size of pits = Small, no wider than the parapsidal line; and
    20. (Thorax) scutum, surface appearance = Lines between pits essentially smooth and evenly raised around pits, NOT craggy.