Environment

Wild bees have been found building nests entirely out of plastic waste

In the crop fields of Argentina, bees have been building nests for their young out of some strange materials. For the first time, scientists have found bee nests made entirely out of plastic waste.

A lot of plastic in the form of packaging comes into farms, and often makes its way into the landscape. The world is changing, and wildlife is having to adapt – but whether they can adapt fast enough to keep up with human impact is still up for debate.

Researchers from Argentina’s National Agricultural Technology Institute discovered the plastic nests as part of their research into chicory pollinators.

The team had set up 63 trap nests around crop fields: these are a bit like those bee hotels that you can build in your backyard for solitary bees, with long, hollow tubes, similar to the honeycomb holes where bee larvae grow.

Bees can line these cavities with materials they forage such as mud, leaves, stone, petals and resin. They build these materials into a cosy nest in the cavity, separated into brood cells along the length, each of which holds a growing bee larva.

Over the spring and summer of 2017 and 2018, the team checked their trap nests monthly to look for signs of bee activity.

They only found three nests the bees used. Two were built with mud and petals, and five healthy adult bees emerged from them.

The third had three cells entirely constructed out of plastic, carefully cut into oblong and oval shapes by the bee, and arranged in an overlapping manner. The first two cells were constructed of thin, light blue plastic, similar to a plastic shopping bag. The third cell was made of thicker white plastic.

bee nestClockwise: Plastic waste caught in a fence; plastic bee nest; the pieces of plastic; the cells. (Allasino et al., Apidologie, 2019)

“Among the three cells,” the researchers wrote in their paper, “one contained a dead larva; from the other, the adult seemed to have emerged from the nest; and the third cell was not finished.”

So, of the two occupied cells, one larva died and the other grew to adulthood – indicating that plastic might not be the best choice of building material, but it might not be the worst, either.

The team were unable to make a positive identification of the bee that had built the nest, but believe it may have been an alfalfa leafcutter bee (Megachile rotundata). This is an introduced European species the team had previously seen in the study site, and its lifestyle fits.

It’s a solitary bee that, true to its name, cuts leaves to line its nests, similar to the manner in which the plastic fragments were trimmed. And, in North America, scientists have documented this particular bee using plastic to construct individual brood cells within a larger nest.

What makes this new nest so striking is that all the cells in the nest were constructed of plastic; and it’s the first documented case where two different types of plastic were used.

And it might not actually be bad news. It could, the researchers said, mean that bees have an adaptive flexibility that will allow them to keep up with rapid environmental changes.

Or it might mean that herbicides used in fields are reducing the number of plants the bees prefer to use in their nests. Or, because the bee in this instance only used plastic, without any leaves, it prefers that material for another reason – maybe plastic provides an adaptive advantage we are unaware of, the way some birds use cigarette butts to repel parasites.

It’s impossible to tell from a single nest.

“However,” the researchers wrote, “it could highlight bees’ response capacity in the search for alternative materials for the construction of their nests in the face of human disturbance.”

The research has been published in Apidologie.

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