Some solitary urban bees use plastic or window sealant in nest construction.
"We found two solitary bee species using plastic in place of natural nest building materials, which suggests innovative use of common urban materials.
Figuring out that the bees were using plastics in place of natural materials took some detective work by U of G's Andrew Moore, supervisor of analytical microscopy at Laboratory Services.
Moore analyzed a grey "goo" that MacIvor discovered in the nests of one kind of bee, Megachile campanulae, which uses plant resins to build its nests,...
Turns out that M. campanulae was occasionally replacing plant resins with polyurethane-based exterior building sealant, such as caulking, in its brood cells--created in a nest to rear larva.
The researchers also discovered another kind of bee, Megachile rotundata, an alfalfa leafcutter, was using pieces of polyethylene-based plastic bags to construct its brood cells. The glossy plastic replaced almost one-quarter of the cut leaves normally used to build each cell.
Markings showed that the bees chewed the plastic differently than they did leaves, suggesting that the insects had not incidentally collected plastic. Nor were leaves hard to find for the bees in the study.
"The plastic materials had been gathered by the bees, and then worked -- chewed up and spit out like gum -- to form something new that they could use," Moore said.
In both cases, larvae successfully developed from the plastic-lined nests. In fact, the bees emerged parasite-free, suggesting plastic nests may physically impede parasites, the study said. [emphasis mine]