2011 Volume 62 Issue 2 Pages 57-63
The blue pansy, Junonia orithya orithya (Lepidoptera, Nymphalidae), was reared under a photoperiod of 12L-12D (short day) at 20 or 25℃ or under 16L-8D (long day) at 20, 25 or 30℃, and larval development, seasonal polyphenism and cold hardiness were examined. The mean duration of larval and pupal stages decreased significantly with increase in temperature. The developmental threshold (t_0) and the thermal constant (K) for the larval and pupal stages were 13.7℃ and 208.3 day-degrees, and 13.4℃ and 99 day-degrees, respectively. Although all the adult females maintained under 16L-8D at 20 and 25℃ produced mature eggs one week after emergence, none of those under 12L-12D at 20℃ had produced mature eggs even 14 days after adult eclosion. Adults exhibited seasonal polyphenism in response to the photoperiod and temperature experienced at the larval and pupal stages. Under long-day photoperiods at high temperatures, eyespots developed on the ventral surface of the hind wing in both sexes, with an orange pattern also appearing on the dorsal surface of the hind wing in females only (long-day form). In contrast, under short day at low temperature, the eye spots were obscure and the dorsal surface of the hind wing was usually blue in females (short-day form). The supercooling points for larvae, pupae and adults were approximately -12, -17 and -20℃, respectively, irrespective of photoperiodic conditions.
