Seasonal changes in the hormonal regulation of life history traits are recognized as an important aspect of life history adaptation and have attracted considerable attention. Yet, corresponding daily cycles in hormones and life histories have barely been investigated. This topic will be reviewed with particular focus on the dramatic morph-specific daily cycle in the blood titer of juvenile hormone (JH) in morphs of the cricket Gryllus firmus that differ in life history. Recent transcriptome profiling indicates that the morph-specific JH circadian rhythm is associated with extensive morph-specific cycles of gene expression. Failure to investigate daily variation in endocrine and molecular traits not only results in the failure to recognize an important aspect of adaptation, but also can lead to serious errors in interpreting the adaptive basis of observed variation.