Yellow and orange flagging were found in Douglas, Arizona, the USA that had clear circular pieces removed from the margins of the flagging (Fig. 1). These markings are nearly identical to the markings made by Megachile leaf-cutter bees when cutting out pieces of leaves to use in nesting material (Fig. 1). We can therefore speculate that the plastic material was cut by Megachile bees, presumably to use in their nests. The first observation occurred in July of 2009, where yellow flagging was found with 18 distinct putative bee-made holes. The second observation was in September of 2019, where orange flagging was found with eight semicircles removed, and two pieces partially removed.
The impact of this plastic flagging on leaf-cutter bee larvae is not directly known as adult bees from these nests have not been observed. One prior publication suggested that plastic use could be an “ecologically adaptive trait” in response to increasing anthropogenic plastic pollution. We hesitate to draw a similar conclusion— An ecological adaptation, by definition, should increase the fitness of the bee exhibiting the trait, compared to that of bees without the trait. Because experiments comparing fitness levels have yet to be performed, it seems early to consider this an adaptation. Moreover, what scant evidence we do have about bees and plastic hint at the possibility that this behavior is not advantageous at all— it has been shown that when Megachile built their nests in plastic straws they experience up to 90% mortality because of moisture problems that resulted in increased mold growth. Plastic use by bees appears uncommon, though reports of it are increasing. Because its effects are unknown, it would be beneficial if citizen scientists and others could watch for additional instances and record them in digital inventorying databases (e.g. iNaturalist.org), as a precursor to more in-depth analyses.
