Did you ever see perfect circles cut for your rose leaves or even flowers? Did you wonder who was responsible? Did you ever imagine it might just be a bee? All Whole Leaf Piece plugs are made by Megachile, though not all Megachile make whole leaf piece plugs (some use resin or chewed vegetation). You could say that Megachile are the ultimate leaf-cutting bee.
Whole leaf piece plugs are made from circles of leaf, often several overlapping, but sometimes just one solid piece is visible. They can be loosely packed or “glued” into place. The veins and often hairs are visible on the pieces of leaf. Although they usually start out green, they will fade with time. A variation of this are the bees that cut, not from leaves, but from petals. Instant potpourri.
We have a number of Megachile that plug with whole leaf or petal pieces around Colorado. These vary in size from small to large. You can find them in all hole sizes except the smallest ones. They’re starting to nest now and you’ll get to see them throughout the rest of the summer: some species have more than one generation, so watch your whole leaf piece plugs for holes. When you see holes, please submit those data, because that tells us your bees have successfully reproduced. Then you can watch for the daughters to reuse the nests. We have had as many as 3 consecutive Megachile nests in a single tunnel: Moms, daughters, and granddaughters!
Megachile rotundata, the alfalfa leaf-cutting bee, is a European species that was accidentally introduced to the United States, but is now managed for pollination in alfalfa seed production fields. They’ve done well enough for themselves that they’re incredibly widespread. This is a common species in our bee blocks.
We also have many NATIVE species that nest in our bee blocks. Megachile inermis, one of Colorado’s largest Megachile species, is found at higher elevations. When not provided with a bee block to nest in, this species will nest in aspen logs and often use decaying wood in their plugs along with whole leaf pieces.
Another smaller native species is Megachile relativa. These bees have a beautiful orange scopa, the pollen carrying hairs on the underside of their abdomen.
Our Megachile that plug with whole leaf pieces also line their cells with leaf pieces, like wallpaper for the nursery.
AND – if you participated in the project last year (thank you!) you may remember reading about Coelioxys, the leaf-cutting cuckoo bees. These bees sneak into a Megachile nest and use their pointy abdomens to slit the cell’s leaf lining and deposit an egg of their own. Coelioxys eggs aim to hatch before the rightful nest occupants, so that they can mature faster and eat all the food stores right out from underneath the original occupants.