Low developmental threshold temperature and thermal constant of an endangered butterfly Panchala ganesa loomisi (H. Pryer) (Lepidoptera, Lycaenidae)

Abstract

To calculate the low developmental threshold temperature (T₀) and thermal constant (K), eggs, larvae, and pupae of an endangered butterfly Panchala ganesa loomisi were reared at several different temperatures. The T₀ and K were 10.00 °C and 61.67 degree-days for egg development, 10.64 °C and 256.87 degree-days for larval development, 11.32 °C and 162.61 degree-days for pupal development, respectively. Using these parameters, the possible number of generations produced per year in Kasugayama (extinct population) and Boso Peninsula (extant population) were estimated. In Kasugayama, three generations could have been produced per year under the temperature conditions around 1960 when this butterfly species was present, and the seasonal occurrence of each generation roughly matched the past descriptions. In Boso Peninsula, this butterfly may have produced four generations per year under the temperature conditions of 2010s if were multivoltine, while the Boso population was thought to produce only one generation per year (univoltine) based on current findings. The factors limiting the number of generations of this endangered butterfly are discussed.