Figure 4.

Bar graphs illustrating the influence of amine receptor blockers on (a) level of aggression and (b) fight duration after residency (circle/bold line, median; bar, i.q.r.). The crickets were treated prior to the initial fight with either vehicle (white bar), propranolol (stippled bar), yohimbine (upwards-hatched bar), phentolamine (downwards-hatched bar) or epinastine (cross-hatched bar). The aggressiveness of treated animals was evaluated in an initial fight (naive versus naive) and in a second contact 15 min later before which the losers remained in the area without a shelter (control-loser versus intruder) or with a shelter that they always occupied (resident-loser versus intruder, grey background). n is given in parentheses beneath each column, excepting initial fight, which is pooled. Asterisks denote statistically significant differences (for unpaired datasets: Mann–Whitney U-test).