Science

Leaf-Cutter Bees Use Plastic in Nest Construction, Study Says

Leaf-cutter bees, members of the genus Megachile, are among the most recognizable solitary bees due to their habit of cutting out small circles of leaves to use in nest construction. In a new paper, Utah State University evolutionary ecologist Joseph Wilson and colleagues report new evidence of leaf-cutter bees using cut pieces of plastic.

Examples of leaf-cutter bee use of a sumac leave and two pieces of plastic flagging. Image credit: Wilson et al.

Examples of leaf-cutter bee use of a sumac leave and two pieces of plastic flagging. Image credit: Wilson et al.

Most bee species are solitary and construct nests in cavities, either in the ground or in pre-existing tunnels in wood.

The nesting in the wood often augments their nests with plant material. In particular, leaf-cutter bees are known for cutting semi-circular pieces out of leaves to line their nests.

While leaves from a variety of plant species are used for nesting material by these bees, several recent publications highlighted observations of Megachile species using plastic waste instead. They suggested such behavior could be an ecologically adaptive trait and a beneficial recycling effort.

“Not so fast. Just because bees can use plastic, doesn’t mean they should,” Dr. Wilson said.

“Leaf-cutter bees are among the most recognizable of solitary bees, because of their habit of cutting circles out of leaves to build their cylindrical nests,” he added.

“We’ve heard reports of these bees using plastic, especially plastic flagging primarily in construction and agriculture, and we decided to investigate.”

In Douglas, Arizona, the researchers found yellow and orange flagging that had clear circular pieces removed from the margins of the flagging.

Those markings were nearly identical to the markings made by leaf-cutter bees when cutting out pieces of leaves to use in nesting material.

The authors speculate that the plastic material was cut by these bees, presumably to use in their nests.

“Building from plastic could change the dynamics and environment of the bee’s nest cells, because plastic doesn’t breathe like natural materials,” Dr. Wilson said.

“In the 1970s, some researcher let leaf-cutter bees nest in plastic straws and found 90% of the bees’ offspring died because of fungal growth. The plastic sealed in the moisture and didn’t allow gas exchange.”

To deter bees’ use of flagging, the team suggests use of fabric ribbons made from natural fibers.

“These materials are biodegradable and, if used by bees, will likely avoid the harmful moisture-capturing effects of plastic,” Dr. Wilson said.

The team’s paper was published in the journal Science Matters.

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Joseph S. Wilson et al. Evidence of leaf-cutter bees using plastic flagging as nesting material. Science Matters, published online October 9, 2020

Lohit Soundarajan

Founder , Editor Tech Guy #Voxguy

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