Labellar Structure of the <i>Maxillaria splendens</i> Alliance (Orchidaceae: Maxillariinae) Indicates Floral Polyphenols as a Reward for Stingless Bees
2023
Kevin L. Davies | Emerson R. Pansarin | Małgorzata Stpiczyńska
Several studies have reported stingless Meliponini bees gathering hairs from the labella of <i>Maxillaria</i> spp., including <i>M. ochroleuca</i>, a member of the <i>M. splendens</i> alliance. Such hairs usually contain food materials and are thought to have nutritional value. The papillose labella of representatives of the <i>Maxillaria splendens</i> alliance, however, bear scattered, simple 1-5-celled uniseriate trichomes (hairs) that lack food materials. By contrast, here, as well as polyphenolic compounds, typical labellar papillae usually contain small quantities of starch, protein, and minute droplets of lipid, the last probably involved in the production of fragrance. Towards the labellum apex occur elevated groups of papillae that lack food materials, but contain volatile compounds, probably fragrance precursors. In the past, the terms ‘trichomes’ or ‘hairs’ and ‘papillae’ have been used interchangeably, causing some confusion. Since the trichomes, however, unlike the papillae, are easily detachable and can fragment, it is most likely they, not the papillae, that have previously been observed being collected by bees, but their poor food content indicates that they do not function as food-hairs. Even so, our field observations of <i>M. ochroleuca</i> reveal that stingless bees scrape polyphenol-rich labellar tissue and possibly use this material to produce a resinous, complex, heterogeneous substance commonly referred to as ‘bee glue’, used for nest construction and repair.
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