Characterizing Honeybee Cuticular Hydrocarbons During Foraging

Honeybees (Apis mellifera) adjust their time and effort during foraging activity. Their metabolic rates together with body temperature rise while gathering profitable resources. These physiological changes may result in a differential cuticular profile, which in turn may bear communicational value. We evaluated if sucrose concentration of collected food affects the cuticular chemistry of honeybees during foraging. We trained bees to artificial feeders with high (2 M) and low (0.5 M) sucrose concentrations, and captured the active foragers for surface extraction of cuticular compounds. We sampled foragers just after feeding, before taking-off towards the hive, and upon landing at the hive entrance, before entering the hive. Through gas chromatography-mass spectrometry analysis of cuticular extracts, we identified and quantified 48 compounds, including cuticular hydrocarbons (CHCs) and volatiles associated with exocrine glands. We found that higher sucrose concentrations resulted in increased amounts of alkanes and alkenes in the surface extracts of foragers captured at the hive entrance, but not at the feeding site. Our results suggest that the differences that have been reported for CHCs in waggle-dancing honey bees can be already found once they return to the hive from profitable food sources.

Behaviour-locked signal analysis reveals weak 200–300 Hz comb vibrations during the honeybee waggle dance

Waggle-dancing honeybees produce vibratory movements that may facilitate communication by indicating the location of the waggle dancer. However, an important component of these vibrations has never been previously detected in the comb. We developed a method of fine-scale behavioural analysis that allowed us to analyze separately comb vibrations near a honeybee waggle dancer during the waggle and return phases of her dance. We simultaneously recorded honeybee waggle dances using digital video and laser-Doppler vibrometry, and performed a behaviour-locked Fast Fourier Transform analysis on the substratum vibrations. This analysis revealed significantly higher-amplitude 200–300 Hz vibrations during the waggle phase than during the return phase (P=0.012). We found no significant differences in the flanking frequency regions between 100–200 Hz (P=0.227) and 300–400 Hz (P=0.065). We recorded peak waggle phase vibrations from 206 to 292 Hz (244+/−28 Hz; mean +/− s. d., N=11). The maximum measured signal - noise level was +12.4 dB during the waggle phase (mean +5.8+/−2.7 dB). The maximum vibrational velocity, calculated from a filtered signal, was 128 microm s(−)(1) peak-to-peak, corresponding to a displacement of 0.09 microm peak-to-peak at 223 Hz. On average, we measured a vibrational velocity of 79+/−28 microm s(−)(1) peak-to-peak from filtered signals. These signal amplitudes overlap with the detection threshold of the honeybee subgenual organ.