Honeybees are finicky foragers when it comes to searching for nectar — and for good reason. Some flowers provide a heartier meal; others are dangerous when honeybees land on them. How do honeybees distinguish nectar-bearing from non-nectar-bearing flowers and safe from dangerous flowers? With “photographic images,” says biologist James Gould at Princeton (N.J.) University. Gould’s experiments, reported in the March 22 SCIENCE, show as low-resolution images, contradicting earlier studies that suggested bees remember only isolated features of flowers, such as prominent line angles or the ratio of edge to area. “The old idea,” Gould says, “is that they remember a checklist of characteristics — much like a description of a murder suspect whose hair and eye color are know, but with no photograph.” Gould’s data indicated that honeybees can remember how flower parts are arranged in relation to each other, a feat possible only when photographic images, not isolated features, are remembered.
In his experiments, honeybees were given a choice between two similar patterns that differed only in the spatial relationship between their parts. One of the patterns provided a sugar reward, the other did not. After being reinforced on the pattern providing the sugar, the bees were offered the same patterns in another trial. This time the patterns’ positions were reversed, and neither provided a reward. Yet in most cases bees chose the pattern on which they had been reinforced in the previous trial, suggesting that they had remembered the spatial relationships of the elements in the pattern. Honeybees’ ability to distinguish different flowers and flower parts can help them avoid dangerous situations. For example, alfalfa blossoms’ unusual arrangement of petals and stamen can be fatal to honeybees.
The pollen-bearing stamen of an alfalfa blossom is covered by a central petal. When an insect lands on the flower, the petal releases the stamen and sweeps pollen upward to facilitate pollination. The mechanism is adaptive for large insects, but honeybees trying to pollinate unopened flowers will be jolted off or trapped inside the central petal. In a separate experiment, Gould showed that honeybees quickly learn to distinguish opened from unopened flowers, showing that they have good pictorial memory.” The studies show that many scientists’ “presumptive vertebrate-invertebrate dichotomy is false,” Gould says.
But in order to truly bring vertebrate bias down to size, Gould will have to show that honeybees have size constancy — the ability to remember something they first saw close up when they later see it from farther away.