Results
Outbreak of the modified forms in Fukaura
Zizeeria maha is generally considered to be vulnerable to low temperature conditions [11,12]. Hence, the recently reported northward range expansion of this species [7,8] led us to investigate recent temperature dynamics in Fukaura. The highest temperatures in Fukaura had steadily increased year by year since 1996 until 2000 (Fig. (Fig.1B),1B), which probably encouraged the range expansion of Z. maha to the north. On the other hand, a large amount of snowfall in Fukaura did not discourage this range expansion (not shown).