75.
Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a
rich food source. Recent studies have shown that
Trigona and
Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus
Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking,
we studied the glandular origin of the trail pheromone of
Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent
trail deposited by their nestmates only when they were baited with extracts from the foragers’ labial glands. Compounds extracted
from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone
of
G. mombuca is produced in the labial glands, as in
Trigona and
Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers’ mandibular glands, which disproves
its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl
butanoate as major constituent. We, therefore, postulate that the trail pheromone of
G. mombuca is composed of a blend of esters.
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