Mystery of the Swiss Cheese Leaves
In recent weeks, we've been noticing more and more leaves around the garden which look as though someone's been going around hole-punching them. And while seeing punctured foliage usually elicits a sense of concern about pests and disease, something about the smooth, skillfully-crafted shape of these holes makes them seem benign to me... artful even!
Whoever's responsible seems to be especially fond of lilac leaves
The snowberry seems to be a favorite as well!
Oho! Could this bee the culprit?
Indeed, these holes are the work of a leafcutter bee (genus 'Megachile', which means “large jaws”) — a short-living, but very important pollinator which uses leaf or flower cuttings to construct little cigar-shaped nests for her offspring. Within each nest are separate rooms (cells) for each larvae, where the mother also leaves bee bread which the brood eat as they grow.
Although leafcutter bees' activities damage leaves, their short harvest period doesn't usually significantly harm the long-term health of plants. Furthermore, their ecological value as pollinators arguably outweighs the aesthetic value of ornamental plants (where these holes tend to cause the most concern).
I managed to capture a short video of this hardworking mama gathering nest material which you can view below: