Semiochemical-based food-foraging in German cockroaches, Blattella germanica L. (Dictyoptera: Blattellidae)

In two-choice, still-air arena olfactometer experiments, Porapak-Q headspace volatile extract of peanut butter and solvent extract of beer were shown to attract males of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae). Coupled gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric (MS) analyses of these attractive extracts, or fractions thereof, and of synthetic standards, revealed many candidate semiochemicals. Elaborate olfactometer experiments determined that 1-hexanol from peanut butter, and ethanol and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP) from beer, are the key semiochemicals of these food sources. 1-Hexanol is a well known headspace volatile of decomposing lipids, ethanol conveys food fermentation, and DDMP with a caramel-type flavor has been found in many types of (heated) food. By responding to these rather general food-derived compounds, the omnivorous German cockroaches appear to exploit semiochemicals that indicate the presence of various food types, such as lipids and carbohydrates.