At nearly an inch in length (24 mm), Megachile sculpturalis is the largest Megachilid in the North America. Native to Asia, it was recently (i.e. 1990s) accidentally introduced into the United States. It has rapidly spread, but aside from some possible competition with carpenter bees for nest sites, the ecological impacts of this, and other, non-native bees (such as Lithurgus chrysurus) are unknown.
There is a funny little anecdote about the nest site competition from Laport and Minckley 2012 (Xylocopa virginica is the carpenter bee):
“On 23 July, we observed three X. virginica on the ground below the carport (though, not directly below the openings of the nests). All three X. virginica had worn wing edges, suggesting they had been actively foraging (second-year) females, and none attempted to escape from where they were originally found despite light prodding. Close inspection of all three individuals revealed they were irregularly covered in a sticky resin. Although the resin encumbering these X. virginica could have come from resin pockets within the wooden beams, this seems unlikely as the beams of the structure were oven-dried and several years old. Additionally, these individuals were probably from different nests that were ca. 0.5 m apart, making it unlikely that all three of these individuals encountered a resin pocket in separate nests.”
Obviously, the implication that the authors are trying to make is that the Giant Resin Bees drove the carpenter bees out by attacking them with resin.
The other potential detrimental effect of the Giant Resin Bee is that it readily pollinates Kudzu, a rather nasty invasive vine.
The other day, my hiking buddy and I were walking and I stopped suddenly in the middle of the path, stooped down, and scooped up a dead insect. My buddy is pretty used to this by now, so he waited patiently.
“Ooo,” I exclaimed, “It’s a Megachile sculpturalis!”
He raised an eyebrow, “Is that…important?”
“I have never seen one before,” I said, “It is the largest Megachilid in North America.” I held its body gently in my cupped palm. “I’m keeping it,” I said fiercely.
“Ooooh…kay…” he said. I carried it the remaining four miles home, and when we parted ways, he said, “Enjoy your bee.”
And I have.