Fruit flies respond more effectively to danger when in a group

Fruit flies respond more effectively to danger when in a group. A research team discovered this behavior as well as the neural circuits which relay this information, opening a new field of research. Flies exposed to a stress signal when in a group adopt a more effective response than isolated insects, found researchers at UNIL and EPFL. These typically solitary dipterans interact to generate a coherent collective response. "Interaction within the group increases their sensitivity to the environment, which facilitates decision making," says Pavan Ramdya, lead author of a paper published today in Nature. To explore this behavior, the researchers began by quantifying the presence of CO2 avoidance strategies. This gas, odorless to humans, represents a danger signal to the flies. A drosophila flying alone makes little effort to avoid the aversive odor. In a group, a significant proportion of flies leave the area within a few seconds. Even deprived of their sense of smell, flies in a community with unmodified peers continue to go quickly to the good, clean air. Since the genome of drosophila is fully sequenced, a database comprising genetically modified flies is also available. It is therefore possible for scientists to select for certain characteristics, such as lack of olfactory genes. By observing the flies, the researchers found that this group behavior was preceded by numerous close between the insects. Specifically, it is through small touches on the legs that the avoidance behavior is strengthened. This serves as genuine communication in code as it also indicates the direction to follow. A nudge on the right leg from a peer, and the fly goes left. With a touch on the left, it heads right. So does a fly-leader need authority to indicate the route to follow?