Animal flavoproteins called cryptochromes (CRYs) are generally believed to have distinct circadian clock functions in insects and mammals. We have discovered that the monarch butterfly, Danaus plexippus, has two cry genes: one encodes a fly-like protein with photosensitive properties, while the other encodes a mouse-like protein with potent transcriptional repressive activity. Database searches show that other non-drosophilid insects also have two cry genes. These findings change our view of how some insect clocks may work and redefine the evolution of animal CRYs

This article derives from a society-wide symposium organized by Timothy Bradley and Adriana Briscoe and presented at the 2009 annual meeting of the Society for Integrative and Comparative Biology in Boston, Massachusetts. David Grimaldi provided the opening presentation in which he outlined the major evolutionary events in the formation and subsequent diversification of the insect clade. This presentation was followed by speakers who detailed the evolutionary history of specific physiological and/or behavioral traits that have caused insects to be both ecologically successful and fascinating as subjects for biological study. These include a review of the evolutionary history of the insects, the origins of flight, osmoregulation, the evolution of tracheal systems, the evolution of color vision, circadian clocks, and the evolution of eusociality. These topics, as covered by the speakers, provide an overview of the pattern and timing of evolutionary diversification and specialization in the group of animals we know as insects.