title: Body size limits dim-light foraging activity in stingless bees (Apidae: Meliponini).
abstract: Stingless bees constitute a species-rich tribe of tropical and subtropical eusocial Apidae that act as important pollinators for flowering plants. Many foraging tasks rely on vision, e.g. spatial orientation and detection of food sources and nest entrances. Meliponini workers are usually small, which sets limits on eye morphology and thus quality of vision. Limitations are expected both on acuity, and thus on the ability to detect objects from a distance, as well as on sensitivity, and thus on the foraging time window at dusk and dawn. In this study, we determined light intensity thresholds for flight under dim light conditions in eight stingless bee species in relation to body size in a Neotropical lowland rainforest. Species varied in body size (0.8-1.7 mm thorax-width), and we found a strong negative correlation with light intensity thresholds (0.1-79 lx). Further, we measured eye size, ocelli diameter, ommatidia number, and facet diameter. All parameters significantly correlated with body size. A disproportionately low light intensity threshold in the minute Trigonisca pipioli, together with a large eye parameter P eye suggests specific adaptations to circumvent the optical constraints imposed by the small body size. We discuss the implications of body size in bees on foraging behavior.
authors: Department of Evolutionary Biology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria. martin.streinzer@univie.ac.at.|Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria. martin.streinzer@univie.ac.at.
authors: Martin
authors: http://orcid.org/0000-0002-6656-7224
authors: M
authors: Streinzer
authors: Department of Botany and Biodiversity Research, Faculty of Life Sciences, University of Vienna, Rennweg 14, 1030, Vienna, Austria.
authors: Werner
authors: W
authors: Huber
authors: Department of Evolutionary Biology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.|Behavioral Physiology and Sociobiology, Biozentrum, University of Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors: Johannes
authors: J
authors: Spaethe
mesh_terms: D000818:Animals; D001516:Bees / Q000502:physiology*; D049628:Body Size / Q000502:physiology*; D008027:Light; D054817:Pollination / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*
keywords: Body size; Compound eye; Light intensity threshold; Meliponini; Vision