Synchronized, mass-emergences of a yucca moth, Prodoxus Y-inversus (Lepidoptera: Prodoxidae), after 16 and 17 years in diapause.

In 1985 and 1986, more than 180 adults of Prodoxus y-inversus Riley eclosed from cocoons of the 1969 generation in Yucca baccata, after prepupal larvae spent 16 and 17 years in diapause, intervals prior to mass emergence that are unmatched by any other insect on record. The emergences, which occurred during 15- to 16-day periods, followed many years of virtually no maturation by other individuals of the colony, and the size of the moths was not diminished by the long wait. Successful delay of development and synchronous emergence by many individuals indicates that whole populations can postpone activities through long periods of conditions that would be adverse for adult activity.