First record of microfibers associated with insects in the Amazon: social wasps (Hymenoptera: Vespidae)

The widespread release of synthetic microfibers into the environment poses a growing threat to biodiversity, including insects that interact closely with airborne and surface particles. Social wasps, known for using plant fibers to build their nests, may incorporate these synthetic materials into their colony structures. This study investigated the presence of non-vegetable fibers in the nests and digestive tracts of four social wasp species - Polybia rejecta (F.), Polybia bistriata (F.), Polybia sericea (Oliver) and Polistes canadensis (L.) - collected from distinct sites in the Amazon region of Brazil. Microscopic analysis revealed non-vegetable fibers, varying in color and measuring 1–16 mm, embedded in both the envelopes and combs of the nests, including structures with larvae. No synthetic fibers were found on the surface of nests or in the gut contents of dissected adult females. These findings represent the first record of synthetic fiber incorporation by insects in natural Amazonian environments. While ingestion was not confirmed in adults, the incorporation of these materials into nest architecture suggests a widespread environmental presence and raises concerns over potential sublethal effects on social wasps. This shows the potential of social wasps as bioindicators for monitoring microplastic pollution in tropical ecosystems.