Official websites use. Share sensitive information only on official, secure websites. Like many insects, bumblebees use polarized light PL to orient and navigate. The celestial PL pattern is strongest when the sun is close to the horizon, during the dim light of dawn and dusk. In the dim light, the sensitivity of the compound eyes may not be sufficient for detecting PL or landmarks, and it has previously been hypothesized that bumblebees rely on PL from their more sensitive ocelli to navigate at dawn and dusk.
Here, we tested this hypothesis using a combination of electrophysiological and behavioural tests. Specifically, we investigate whether bumblebee ocelli can detect PL and explore how the PL contribution from the ocelli and compound eyes is affected by light intensity.
We find that bumblebee ocelli do indeed have PL sensitivity and that PL information can be used to guide behaviour in dim light. In bright light, however, both the compound eyes and ocelli are important for the detection of PL.
Our results support the hypothesis that bumblebees use PL information from the ocelli at the low light levels that occur around dawn and dusk, and this may support their ability to forage during these periods. The sky provides insects with several cues for orientation and navigation. One of the most important of these cues is the pattern of polarized light PL that is generated in the sky when sunlight is scattered by the atmosphere and that moves with the sun throughout the day [ 1 ].
To detect PL, insects have specialized photosensitive structures known as rhabdoms that contain two untwisted photoreceptor cells that are located in the dorsal rim area DRA of the compound eyes [ 2 — 4 ]. Rhabdoms that satisfy the anatomical requirements for PL sensitivity have also been found in the dorsally located simple camera-type eyes called ocelli in some insects [ 5 — 9 ].
