Chemical communication in raids of the robber bee

What is it about?

Most social bees collect floral resources to obtain proteins and carbohydrates. However, the obligate cleptoparasite stingless bee Lestrimelitta limao, the so-called robber bee, is a rare exception as it collects resources by raiding other stingless bee nests. The mechanisms these bees use to overcome host colony defenses are poorly understood. Many host species retreat inside the nest during L. limao attacks and the signals triggering this behavior require a better understanding. While some researchers have proposed that robber bees release chemical compounds that are responsible for host retreat, others have hypothesized that the observed behavior results from communication among host workers. In order to investigate the role of interspecific signals in raids, we tested the effects of robber bees’ mandibular and labial gland secretions on the behavior of Frieseomelitta varia workers. We combined behavioral assays with chemical and electrophysiological analyses. We found that citral and 9-nonacosene are major mandibular gland compounds and two esters, hexadecyl acetate and 9-hexadecenyl acetate, are major labial gland compounds. These three major compounds elicited electro-physiological responses on host worker antennae. Robber bee labial gland extracts repelled both foragers and guards, while mandibular gland content increased aggression. Our results suggest that interspecific communication plays a role during natural raids and that esters from L. limao labial glands, rather than citral, are more likely to trigger the host retreat. The results add to our knowledge about L. limao chemical communication and help to elucidate the mechanisms involved in their intriguing foraging strategy.

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