Honeybees can learn the relationship between the solar ephemeris and a newly experienced landscape: a confirmation

The brain behind straight-line orientation in dung beetles

For many insects, celestial compass cues play an important role in keeping track of their directional headings. One well-investigated group of celestial orientating insects are the African ball-rolling dung beetles. After finding a dung pile, these insects detach a piece, form it into a ball and roll it away along a straight path while facing backwards. A brain region, termed the central complex, acts as an internal compass that constantly updates the ball-rolling dung beetle about its heading. In this review, we give insights into the compass network behind straight-line orientation in dung beetles and place it in the context of the orientation mechanisms and neural networks of other insects. We find that the neuronal network behind straight-line orientation in dung beetles has strong similarities to the ones described in path-integrating and migrating insects, with the central complex being the key control point for this behavior. We conclude that, despite substantial differences in behavior and navigational challenges, dung beetles encode compass information in a similar way to other insects.

The memory structure of navigation in honeybees

The analytical approach to navigation studies aims to identify elementary sensory motor processes that guide an animal to a remote site. This approach will be used here to characterize components of navigation in a flying insect, the honeybee. However, navigation studies need to go beyond an analysis of behavioral routines to come up with a synthesis. We will defend the concept of an active memory structure guiding navigation in bees that is best described as a mental or cognitive map. In our opinion, spatial/temporal relations of landmarks are stored in a mental map in such a way that behavioral routines such as expectation and planning, as indicated by shortcutting, are possible. We view the mental map of animals including the honeybee as an "action memory of spatial relations" rather than as a sensory representation as we humans experience it by introspection. Two components characterize the mental map, the relational representation of landmarks and the meaning of locations to the animal. As yet, there is little data to suggest that bees assign meaning to the experienced locations. To explore this possibility, further studies will be needed, whereby honeybees provide a unique model to address this question.

Interactions of the polarization and the sun compass in path integration of desert ants

Desert ants, Cataglyphis fortis, perform large-scale foraging trips in their featureless habitat using path integration as their main navigation tool. To determine their walking direction they use primarily celestial cues, the sky's polarization pattern and the sun position. To examine the relative importance of these two celestial cues, we performed cue conflict experiments. We manipulated the polarization pattern experienced by the ants during their outbound foraging excursions, reducing it to a single electric field (e-)vector direction with a linear polarization filter. The simultaneous view of the sun created situations in which the directional information of the sun and the polarization compass disagreed. The heading directions of the homebound runs recorded on a test field with full view of the natural sky demonstrate that none of both compasses completely dominated over the other. Rather the ants seemed to compute an intermediate homing direction to which both compass systems contributed roughly equally. Direct sunlight and polarized light are detected in different regions of the ant's compound eye, suggesting two separate pathways for obtaining directional information. In the experimental paradigm applied here, these two pathways seem to feed into the path integrator with similar weights.