RESUMO
Stale beer and peanut butter are effective baits for the German cockroach (GCRs), Blattella germanica (L.) (Dictyoptera: Blattellidae). In still-air arena olfactometer experiments it was previously shown that headspace volatile extracts of peanut butter and solvent extract of beer attract male GCRs. The objective of this study was to identify the semiochemicals that mediate attraction of GCRs to these sources. 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-4H-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 several types of food. By responding to these rather general food-derived compounds, the omnivorous GCRs appear to exploit semiochemicals that indicate the presence of various food components, such as lipids and carbohydrates. Synthetic equivalents of these semiochemicals may be formulated as baits or be added to, and thus enhance the attractiveness of, natural food sources as trap or insecticidal baits.
