Squirting and refilling: Dynamics ofp-benzoquinone production in defensive glands ofDiploptera punctata

Diploptera punctata, a Pacific islands cockroach, discharges a fine aerosol ofp-benzoquinones from a pair of tracheal glands in response to disturbance or CO2 anesthesia. In addition, the glands and their contents are shed at each molt. We measured the amount ofp-benzoquinones discharged in response to pinching and anesthesia and the filling of glands after discharge and molting. Roaches discharge highly variable amounts of quinones but appear to retain approximately 11% of their lifetime total benzoquinone content after repeated discharges. Roaches rapidly fill their glands after molting (18Μg quinone/day) but after discharging appear to refill at a much slower rate or not at all. This lack of refilling could result from an inability to produce quinones after a finite time period or in excess of a fixed quantity. The delayed accumulation ofp-benzoquinone with respect to the alkylated derivatives in newly molted adults suggests competition for aromatic amino acids between cuticular and defensive quinone synthesis.