Navigation without vision: bumblebee orientation in complete darkness

In flight cages, worker bumblebees (Bombus impatiens) spontaneously explore d the surroundings of their nest and foraged in complete darkness by walkin g instead of flying from feeders up to 150 cm away from the nest. This beha viour was wholly unexpected in these classically visual foragers. The findi ng provides a controlled system for dissecting possible non-visual componen ts of navigation used in It also allows us to isolate navigation mechanisms used in naturally dark situations, such as in the nest. Using infrared vid eo, we mapped walking trails. We found that bumblebees laid odour marks. Wh en such odour cues were eliminated, bees maintained correct directionality, suggesting a magnetic compass. They were also able to assess travel distan ce correctly, using an internal, non-visual, measure of path length. Path i ntegration was not employed. Presumably this complex navigational skill req uires visual input in bees.