I have been checking my bee hotel regularly for new residents and I was delighted today to spot a new bee coming out of one of the holes. The chamber was just about complete, but being fairly new to the wonderful world of bees, I was not sure what this species was. I went to get my camera to try to photograph it when it returned. This time, it returned with a huge piece of leaf…. well that was a bit of a clue as to the species! It is a Megachile leaf cutter bee!
The nests of these bees are sometimes constructed within hollow twigs or other similarly constricted natural cavities, but often are in burrows in the ground. Nests are typically composed of single long columns of cells, the cells being sequentially constructed from the deepest portion of the tunnel outwards. The female places a supply of food (pollen or a pollen/nectar mix) and an egg in each cell, then builds a cap and a wall that separates the completed cell from the next one. They bring the pollen in on the hairs underneath their abdomen. They cut the leaves with sharp pincers and carry them back, trimming them and cementing them with saliva.
The larva hatches from the egg and consumes the food supply. After moulting a few times, it spins a cocoon and pupates, often after several months of hibernation as a prepupa. Then it emerges from the nest as an adult. Males, which are typically smaller and emerge in advance of females, die shortly after mating, but females survive for another few weeks, during which they build new nests.
It was fascinating to watch and I managed to get a few pictures with my little Panasonic. There is another one checking out the bamboo canes, lower in my bee hotel. It seemed to be cleaning the bamboo out before starting to lay.