Adult reproductive dormancy in D. melanogaster. In response to cool temperatures and short day lengths, some populations of vinegar flies can undergo a plastic, reversible state of adult reproductive dormancy (often referred to as reproductive diapause). This syndrome is associated with ovarian arrest in females (causing small, nonvitellogenic ovaries, as illustrated in the figure) or arrested spermatogenesis in males, increased levels of stress resistance, and greatly improved adult survival. See main text for further details. Figure credit: Chloé Schmidt (University of Manitoba).