A stingless bee uses labial gland secretions for scent trail communication ( Trigona recursa Smith 1863)

The pheromones used by several species of stingless bees for scent trail communication are generally assumed to be produced by the mandibular glands. Here we present strong evidence that in Trigona recursa these pheromones originate from the labial glands, which are well developed in the heads of foragers. Analysis of the behavior involved in scent marking shows that a bee extends her proboscis and rubs it over the substrate. A single scent marking event lasts for 0.59+/-0.21 s while the bee runs a stretch of 1.04+/-0.37 cm on a leaf. According to choice experiments the bees are attracted by a feeder baited with labial gland extract (84.2+/-6% of the bees choose this feeder) but repelled from a feeder baited with mandibular gland extract (only 27.5+/-13.1% of the bees choose this feeder). They do not discriminate between two clean feeders (49.6+/-3% of the bees at a feeder). 87+/-5.1% of bees already feeding leave the feeder after the application of mandibular gland extract whereas only 6.2+/-4.9% and 2.6+/-4% do so when labial gland extract or pure solvent was applied.