The Drosophilidae are a diverse, cosmopolitan family of flies, which includes fruit flies. Another unrelated family of flies, Tephritidae, also includes species known as "small fruit flies". The best known species of the Drosophilidae is Drosophila melanogaster, within the genus Drosophila, and this species is used extensively for studies concerning genetics, development, physiology, ecology and behaviour. This fruit fly is mostly composed of post-mitotic cells, has a very short lifespan, and shows gradual aging. As in other species, temperature influences the life history of the animal. Several genes have been identified that can be manipulated to extend the lifespan of these insects.