Ants, wasps and bees (Hymenoptera) create a stunning range of nests, many of them so specific to the species that they can be used to identify their makers, as Mike Downes said in his article about black weaver ants.
That’s certainly true of Leafcutter bees (Megachile spp., Megachilidae, Apoidea) and we might even go one step further and identify them by the marks they leave behind when harvesting their nest-building material.
Leafcutters are solitary, not social like our stingless native honey bees (Trigona spp.), honey bees, paper wasps or green ants, and they construct individual cells, provisioning each with pollen before laying an egg in it. If we see a leaf like the one above, with fingernail-sized nearly-round pieces neatly clipped out of its edge, we are looking at the work of a Leafcutter Bee who has carried the pieces off to her nesting site, as in the next two images.
That particular site is in the hollow frame of an old school desk on my verandah, and it’s unusual only in that access to it, past old mud-wasp nests, is so constricted. Other domestic nesting sites include the space between stored boxes or planks, or even the space between the spine of a loose-leaf folder and its pages. In nature, knot-holes and hollow branches are probably the locations of choice. The cell itself looks like a small, stumpy cigar. If there’s space, she will construct a row of them end-to-end like this:
Within each cell, the egg hatches into a pale grub which grows to adult bee size before pupating and finally emerging. The larva in my final image was unlucky: I accidentally wrecked its nest moving some timber, and opened it up to see what was inside when I realised it couldn’t survive.
As if to drive home the variety of nests our Hymenoptera construct, Leafcutters’ nearest relations are Resin Bees, also solitary but building nests of an incredibly tough resin in any suitable hole.
Leafcutter bees are important pollinators. For more about them and our 1600 (yes, sixteen hundred) other species of native bees, visit Aussie Bee.