Behavioral Response of Eocanthecona furcellata to Volatile Compounds from Frass of Larval Spodoptera litura

The predatory stink bug Eocanthecona furcellata exhibits high efficiency in controlling the tobacco cutworm Spodoptera litura. To investigate the role of S. litura larval frass volatiles in prey location by the predatory stink bug, we tested the behavioral responses of adult E. furcellata to fresh frass (from S. litura larvae reared on tobacco leaves and wheat seedlings) using a Y-tube olfactometer. We also extracted, identified and quantified the frass volatiles, and subsequently measured the behavioral responses of adult E. furcellata to individual volatile compounds. The results showed that the frass from 3rd-instar S. litura larvae fed on tobacco was more attractive to E. furcellata than the frass from larvae fed on wheat. Compared with wheat and Chinese cabbage as food sources, the larval frass from tobacco leaves had the highest diversity of compound types and the greatest compound content. Seven individual compounds in larval frass volatiles, including nicotine, neophytadiene, phytol, hexadecanoic acid, linoleic acid, ethyl linolenate, and octadecanoic acid can attract E. furcellata, confirming that these compounds serve as critical olfactory cues for this predatory bug to localize prey at short range.