How Bumblebees (Bombus impatiens) Use Visual Cues of Conspecifics under Stressed and Rewarded Internal States

by Jaime Christiaanse

Supervisor: Dr. Leventa Orban

Abstracts:

Bumblebees are social animals that use visual information about other bees to choose flowers. Workers prefer flowers that are occupied by another bee when the occupier is large relative to the flower, and when occupied flowers are relatively rare in the field compared to empty flowers. Here, we investigate reasons under which the preference for occupied flowers varies with the internal state of B. impatiens workers. To manipulate the workers' internal state, we present workers with a droplet of 1M rewarding sugar solution, 1mM aversive quinine solution, or shake workers for 3s or 10s prior to releasing them into a 12-arm radial arm maze. In Experiment 1, we found significant choice proportion deviations towards occupied patterns in all three conditions: 10s squish (GP = 8:586; p = :004), 3s squish (GP = 18:057; p <:001) and control (no exposure) (GP = 52:159; p < :001). In Experiment 2, there was a significant preference for occupied flowers in sugar exposed workers (GP = 8:025; p = :005), but no preference for occupied flowers in quinine exposed workers (GP = 2:297; p = 0:13). These results suggest that quinine removed the preference for occupied patterns seen in the sugar exposed and squished workers. Previous research has viewed quinine, shaking, and squishing as equivalent manipulations for invoking negative internal states in insects. Our findings indicate that they are not equivalent, since quinine evoked an internal state which drove workers away from their preference for occupied flowers, and squishing did not.