Urban Bees Using Plastic to Build Nests

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Comedian George Carlin once joked that perhaps the Earth wanted plastic, yet didn’t know how to produce it. So, the planet spawned humans only so that we could create the polymer. Two species of leafcutter bee seem to have taken Carlin seriously and now incorporate plastic into their nests.

In Toronto, bees were observed using shreds of plastic bags or dollops of polyurethane sealant to construct some of their nests. Leafcutter bees don’t form hives like honey bees. Instead, solitary females stitch together nests, usually from plant materials.

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A European bee that’s now in Canada, the alfalfa leafcutter bee (Megachile rotundata), normally snips off bits of leaves and flowers to build its nest. In the Canadian study, three out of eight nests from this bee contained bits of plastic bags, an average 23 percent of the construction materials. Course, irregular cut marks on the edges of the plastic suggested that the bees cut them differently than leaves.

The journal Ecosphere published this research, conducted by scientists from York University and University of Guleph.

Another bee, the Canadian native Megachile campanulae, normally collects sticky resins and sap from trees. However, the ecologists discovered polyurethane sealant incorporated into two out of seven of the insect’s brooding chambers.

Although the collection may have been accidental, the ecologists said the bees’ innovative use could be a useful adaptation to a human-dominated ecosystem, since the plastic may supplement scarce supplies of leaves. However, this didn’t seem to be the case, they noted, since several nests contained only leaves and the nests with the plastic also incorporated leaves after the plastic had been glued into place. The bees simply may have used the plastic because of its structural similarity to the materials they naturally use.

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Plastic could have pros and cons for the bees. The plastic bags didn’t stick together like leaves, which the bees chew into a natural glue. The bag-built nests crumbled easily.

On the positive side, the bag-nested bees didn’t suffer attacks from parasites, although the polyurethane-using bees did. Research from the 70s found that when leafcutters nested inside plastic straws, they were safe from parasites, but died from mold because the polymers didn’t let moisture escape.

IMAGE: An alfalfa leafcutting bee (Megachile rotundata) on an alfalfa flower. Credit: U.S. Department of Agriculture