Adhesive trap avoidance in German cockroach, Blattella germanica, American cockroach, Periplaneta americana, and brown cockroach, P. brunnea under laboratory conditions

The capture ratio of adhesive traps for German cockroaches, Blattella germanica, American cockroaches, Periplaneta americana, and brown cockroaches, P. brunnea, was examined every day in a test arena for 8 or 6 days. The capture ratio decreased day by day during the experiments. When nymphs and adult German cockroaches were introduced together at the same time, the males were more easily trapped than the females and nymphs. The females and nymphs of the German cockroach seemed to be more reluctant to cross the sticky surface in consecutive days. The trap ratio was compared between the experienced cockroaches that survived without being trapped for a week and the inexperienced cockroaches that were newly introduced to the test arena from a breeding chamber. The trap ratio of the experienced cockroaches was significantly lower than the inexperienced cockroaches suggesting an escape behavior in experienced cockroaches. Escape behavior was effective to reduce the trap ratio after an interruption period of 5 wk during which the experienced cockroaches were reared without exposure to adhesive traps. Learning of escape behavior to avoid crossing the adhesive surface suggests a possible explanation for trap results.