THE EFFECT OF WIND ON FORAGING ACTIVITY OF THE TENEBRIONID BEETLE LEPIDOCHORA-DISCOIDALIS IN THE SAND DUNES OF THE NAMIB DESERT

The foraging activity of the tenebrionid beetle, Lepidochora discoidal is, was studied in the sand dunes of the Namib Desert. The surface act ivity of this beetle species was found to be correlated both with time of day and wind speed. Higher numbers were observed on the dune surfa ce between 17:00-19:00 h when wind speeds were consistently higher tha n 9 m/s. Noise and vibrations in the dune sand were found to be highly dependent on wind speed. Wind blowing at speeds higher than 5 m/s lif ts the surface sand grains and generates vibrations in the sand. The p eak frequency of these vibrations is in the range of 700-1000 Hz. The vibrational amplitude at the peak frequency is on average 40 dB higher at those wind speeds when the beetles are active compared to lower wi nd speeds. The results indicate that wind is an important cue for thes e beetles and can be perceived by buried beetles through substrate vib rations.