Floral reward production is timed by an insect pollinator

Interval timing--sensitivity to elapsing durations--has recently been found to occur in an invertebrate pollinator, the bumble-bee (Bombus impatiens). Here, bumble-bees were required to time the interval between the start of foraging in a patch of low-quality artificial flowers providing 25% sucrose and the availability of a high-quality flower (HQF) that provided 50% sucrose after a fixed delay. The delay changed after every 20 foraging bouts in the order 30-150-30 s. Bees visited the HQF sooner when the delay was 30 s than when it was 150 s, and visits to the HQF peaked near the end of both delays. When the delay changed to 150 s, bees appeared to time both the previous 30 s delay and the new delay. To examine whether bees also learned what kind of reward was provided at the HQF, its usual reward was replaced with 25% sucrose in a final foraging bout. Bumble-bees rejected the HQF on the reward-replacement test. These results show that bumble-bees remembered both when reward was produced by the HQF and what type of reward was produced. These findings indicate that bumble-bees can learn both the timing and content of reward production.