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Influences of daylength and temperature on the period of diapause and its ending process in dormant larvae of Burnet Moths (Lepidoptera, Zygaenidae)

Auteur : Wipking (Wolfgang)

Année de publication : 1995
Publication : Oecologia
Volume : 102
Fascicule : 2
Pagination : 202-210

Résumé :

The onset of larval diapause in the burnet moth Zygaena trifolii is clearly characterized by the larva molting into a specialized dormant morph. In a potentially bivoltine Mediterranean population (Marseille) two types of diapause can occur within 1 year: firstly, a facultative summer diapause of 3-10 weeks, and secondly, an obligate winter diapause, which can be lengthened by a period of thermal quiescence to several months in temperatures of ltoreq 5 degree C. For the first time, three successive physiological periods have been experimentally distinguished within an insect dormancy (between onset of diapause and molting to the next non-diapause stage), using chilling periods of 30-180 days at 5 degree C, and varying conditions of photoperiod and temperature. These stages are: (1) a continuous diapause-ending process (DEP); (2) thermal quiescence (Q); and finally, (3) a period of postdiapause development (PDD) before molting to the next larval instar. The result of transferring dormant larvae from chilling at 5 degree C to 20 degree C depended on the length of the chilling period. After chilling for 120-180 days, molting to the next instar occurred after 6-10 days, independent of daylength, This period corresponds with the duration of PDD. After shorter chilling periods (90, 60, 30 days and the control, 0 days) the period to eclosion increased exponentially, and included both the latter part of the previous diapause process and the 6-10 day period of PDD. However, photoperiod also influences the time to eclosion after chilling. Short daylength (8 h light / 16 h dark: LD 8/16) lengthened the diapause in comparison to long daylength (16 h light / 8 h dark: LD 16/8). Short daylength had a similar effect during chilling at 5 degree C, as measured by the longer time to eclosion after transfer