Optic flow misdirection experiments provide strong evidence for referential communication in a stingless bee (Melipona panamica)

Canopy level pollination plays an important role in the ecology of tropical forests, yet the mechanisms by which pollinating insects determine canopy height and communicate this information to conspecifics is poorly understood. In the tropical forests of Panama, the stingless bee species Melipona panamica is known to recruit nestmates to food sources at specific distances and heights in the high canopy. In a series of experiments on captive colonies of M. panamica, we found the first evidence of both an optical mechanism for height measurement and for a referential system for the communication of distance information. Our studies determined that M. panamica foragers measure distance through optic flow, a mechanism whereby angular image motion is used to ascertain distance traveled. We then found that optic flow is also used by foragers to measure vertical displacement (height). These results formed the basis for a communication experiment where the optical environment was manipulated to give foragers an exaggerated impression of distance traveled. We found that this information is communicated to inexperienced foragers, who then go to the exaggerated distances, indicating that the information is referentially communicated inside the nest. We have also begun recording sound pulses produced by foragers inside the nest in a new attempt to determine the nature of the signaling method being used. This is the first experiment to provide direct evidence that referential communication may be used by this species, and provides a basis for future work on the use of referential communication of other information, such as direction or food resource quality.