Correlations of head widths between field-collected females and group-reared G1 (A, B) or G2 (C, D) adults at LD 12:12h and LD 16:8h. Each circle indicates the mean value of adults reared in a cage. In (A), mean N = 31.3 and 35.3 in females and males, respectively. In (B), N = 23.3 and 30.0 in females and males, respectively. In (C), mean N = 30.3 and 30.2 in females and males, respectively. In (D), N = 22.0 and 30.6 in females and males, respectively.