Figure 2
Modified individuals obtained from the Fukaura area. Various degrees of modifications were observed, but spot elongation (both inward and outward elongation) and spot reduction (or disappearance) were key features. (A-E) Individuals of the inward-type ...
During this period, the relative population size also increased, albeit more slowly than the percentage of modified individuals. In 2005, the percentage of the modified individuals suddenly decreased. The occurrence of modified individuals from 2000 to 2005 correlates with the overall yearly population size (Pearson correlation coefficient 0.78). These figures, although rough, readily indicate that population-level modifications of Z. maha occurred in Fukaura in 2002, 2003, and 2004.
The color-pattern changes appeared to occur mostly from late August to early October in 2003 (Fig. (Fig.1D).1D). During this period, the average temperature peaked in Fukaura. Similar results were obtained in 2002 and 2004 (not shown). However, high incidence of the modified individuals in summer is likely to be a simple reflection of large seasonal population size in summer (see below).
Classification of the Fukaura individuals: three modification types
The color-pattern modifications found in the Fukaura population can largely be classified into three types (Fig. 2A-O). The first type, "the inward type", shows black spots elongating toward the wing base (Fig. 2A-E). The second type, "the reduction type", shows simple size reduction or loss of spots (Fig. 2F-J). The third type, "the outward type", exhibits black spots elongating toward the outer margin (Fig. 2K-O). Most individuals exhibit symmetrical modifications on both right and left wings in all three modification types. Some exceptional individuals, however, exhibit asymmetrical spot modifications (Fig. 2P-R).