Under the radar: the kleptoparasite Pseudohypocera kerteszi evades meliponine bee defense without cuticular hydrocarbon mimicry or camouflage

Abstract

Pseudohypocera kerteszi is a kleptoparasitic scuttle fly that invades meliponine bee hives, exploiting colony pollen reserves to provision its larvae. Such invasions can precipitate colony collapse, posing a significant threat to meliponiculture in Central and South America. Notably, the flies enter colonies with minimal resistance from typically aggressive guard bees, prompting questions about potential chemosensory or behavioral manipulation. To explore this, we compared the cuticular hydrocarbon (CHC) profiles of P. kerteszi with those of three co-managed meliponine bee species—Melipona scutellaris, Nannotrigona minuta, and Scaptotrigona tubiba—and conducted behavioral assays in controlled arenas and at nest entrances, using S. tubiba as a model species. The CHC profile of P. kerteszi comprises 50 compounds—including n-alkanes, unsaturated hydrocarbons, methyl-branched alkanes, and fatty acyls—with the unique presence of 8,18-heptacosadiene and 10-dotriacontene. In contrast, workers of M. scutellaris, N. minuta, and S. tubiba exhibit profiles dominated by odd-chain alkanes and alkenes, with little or no contribution from alkadienes or methyl-branched alkanes. Bioassays revealed that while S. tubiba guard bees aggressively reject non-nestmates, they tolerate adult P. kerteszi. These findings provide strong evidence against chemical mimicry, camouflage, or insignificance as primary drivers of host acceptance. Instead, the data are consistent with the hypothesis that P. kerteszi utilizes alternative mechanisms, such as physical evasion facilitated by its small size and maneuverability, to prevent the initiation of a full defensive response. This study provides the first chemical characterization of P. kerteszi and narrows the scope of potential evasion strategies, guiding future research on this kleptoparasitic system.