TY - JOUR T1 - Safety in numbers is mediated by motion cues and depends on lobula columnar neurons in <em>Drosophila melanogaster</em> JF - bioRxiv DO - 10.1101/629311 SP - 629311 AU - Clara H Ferreira AU - Marta A Moita Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/05/07/629311.abstract N2 - Being in a group can increase the chances of survival upon an encounter with a predator. This safety in numbers effect allows animals to decrease their defenses when in groups. Despite its wide prevalence, the mechanisms by which group size regulates defensive behaviors remains largely unknown. Here we show that fruit flies displayed a graded decrease in freezing behavior, triggered by an inescapable threat, with increasing group sizes. Furthermore, flies used the cessation of movement of other flies as a cue of threat and its resumption as a cue of safety. Finally, we found that lobula columnar neurons, LC11, mediate the propensity for freezing flies to resume moving in response to the movement of others. Taken together our results suggest that flies rely on motion cues of others to infer danger, allowing a decrease in defensive behaviors when in groups. By identifying neurons implicated in this process this study sets the stage for the search of the neuronal basis of safety in numbers. ER -