Biologists who study the timing of development in insects have focused on variation in duration of pre-adult stages almost without exception. However, development is not complete until adults are not only morphologically mature, but also reproductively mature. Here we describe an experiment in the fruit fly, Drosophila simulans, in which we used artificial selection to create lines with shortened and lengthened duration from eclosion to the age when the first egg was laid. We found significant genetic variation for this trait. The response to selection on age when the first egg was laid was due to variation among females. Delayed adult development was correlated with rapid pre-adult development and longer life span in females. The approach we use here resolves some difficulties with previous approaches used to study the genetics of senescence, and provides an opportunity to study the hitherto unexamined predictions derived from classic models for the evolution of senescence.