Defensive Secretion of the Southern Green Stink Bug (Hemiptera: Pentatomidae) as an Alarm Pheromone

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Abstract
The defensive secretion of the southern green stink bug, Nezara viridula (L.), was found to function as an alarm pheromone by inducing an orthokinetic, nontactic response. Actively secreting individuals and thoracic-gland extracts significantly increased the rate of movement in conspecific individuals, although the response was not oriented with respect to the source of the defensive secretion. The accelerated movement lasted for 2 min, and gland extracts caused a direct dose/response relationship. The rate of turning and net movement were not affected by the scent. A synthetic scent composed of six of the seven major (>1%) components of the defensive secretion significantly increased movement of N. viridula during the first minute of exposure. The single components, E-2-hexenal and E-2-hexenyl acetate, significantly increased movement during the first minute of exposure at doses of 0.1 and 1.0 ¼l, respectively. E-2-hexenal showed an inverse dose/response relationship. The unoriented, increased movement induced by the defensive secretion of N. viridula apparently functions to take the alarmed bug out of the immediate vicinity of the source of the scent, thereby reducing the chance of encounter with the threatening stimulus.