Number of attacks received by ORs and NRs from nonreproductive workers from colony parts 1 () and 2 (▪) (Wilcoxon matched-pair test; ***, P < 0.001; **, P < 0.01; n.s., not significant; observation time: colony A, 210 min; colony B, 230 min; colonies C and E, 420 min; colony D, 240 min).