Australian Resin-Pot Bees: these solitary bees build nesting capsules out of resin, and they often sleep in the capsules as they prepare to lay their eggs
Above: this beautiful photo shows Megachile tarltoni, a type of resin-pot bee, tucked inside an aerial nesting capsule (photo taken by William Menzies)
Bees of the subgenus Austrochile are commonly known as "resin-pot bees," thanks to their unusual nesting habits. A team of entomologists recently described 71 new species from this subgenus, all of which are native to Australia.
Above: more photos of the female resin-pot bee resting in one of her brood capsules
These are solitary bees, meaning that they do not form colonies or live together in hives. Each female creates her own brood cells out of resin, often suspending the chambers from twigs and tree branches. Nesting females have been known to sleep in these aerial chambers while their brood cells are still under construction, and their fuzzy little heads are sometimes seen poking out through the opening at the top.
They also frequently enter the capsules head-first so that they can mold the inner walls of each cell, which means that their rumps are sometimes visible instead.
Above: the same bee is shown with her head tucked toward the bottom of the capsule, providing a glimpse of her rump
The female supplies each capsule with enough nectar and pollen to feed a single offspring until it reaches maturity. She then lays a single egg in each cell and seals the entrance in order to protect the tiny egg as it develops inside.
Once the larva reaches adulthood, it uses its mandibles to cut through the top of the capsule and then emerges as a fully-developed bee.
Above: each of these sealed capsules contains a single egg/larva with enough food to sustain itself until it develops into an adult bee
Resin-pot bees (subgenus Austrochile) are unique to Australia, but several similar resin bees can also be found in Europe and Asia. Anthidiellum strigatum, or the European rotund resin bee, is a similar species from Europe that uses resin to build its brood cells, but it mixes the resin with bits of vegetation, soil, and other debris.
Above: Anthidiellum strigatum, the European rotund resin bee
Many bees build freestanding nests using other methods and materials, as this article explains:
Freestanding nests may be built with mud, resins, stones mixed with resin, plant fibers, and animal fur. Resin bees collect plant-based, sappy resin and use glandular secretions to build hard, water resistant nests. They sometimes decorate the nests with stones and pebbles. An African bee, Serapista, builds nests out of plant fiber, animal fur, and bird feathers glued to plant stems.
Another unique nesting strategy was featured in my previous post about wool-carder bees, which collect the soft, downy fibers from certain plants, bundle them into "cottonballs," and then use that material to build the walls and inner chambers of their nests.
iNaturalist: Photos of Megachile tarltoni
University of Adelaide Newsroom: Australian Scientists Describe 71 New Australian Bee Species
Australian Journal of Taxonomy: The Australian Resin-Pot Bees, Megachile (Austrochile), with Descriptions of 71 New Species
Museum of the Earth: Bee Nesting
