Toktokkies

The "fog-basking" beetle (Onymacris unguicularis) gets its water source from the fog through special biological adaptations. When the fog rolls in at night or early in the morning, these beetles climb to the peak of the dunes, where the water condensation is most dense. The beetle performs a handstand by lowering its head and raising its posterior.^[2] Some beetles have hydrophilic bumps on their back and hydrophobic valleys which make water collection more efficient. The fog condenses on its back and drips into the mouthparts. Through this process, the “fog-basking” beetles can drink 40% of their body-mass.^[3]

The "fog-trapping" beetle (Lepidochora discoidalis) also gets its water from the fog, but it acquires it in a different manner. After foraging for the first half of the night, the “fog-trapping” beetle burrows into the sand. It returns to the surface late at night or early in the morning when the fog rolls across the Namib Desert. It digs a trench into the side of the dune and droplets of water build up on ridges of the trench.^[2] The “fog-trapping” beetles then lick off the droplets of water.

Toktokkies are about 65mm in length and are black or dark brown in color. They are stout, wingless creatures with a tough outer casing.^[4] Although they once had wings, tenebrionid beetles are flightless. Their wings have evolved over time, transferring from separated to move aside for flight to fused on their backs.^[4] Once this evolutionary process occurred, a small cavity was left where the wings used to fold. This has reduced water loss caused by evaporation because the Toktokkies’ respiratory pores now open into this humid cavity, instead of being exposed all the time to the dry air.^[2]

Toktokkies live throughout Namibia. Nearly 20 species have adapted to live in arid climates, like the Namib Desert. Most species inhabit slipfaces and valleys between dunes, searching for the sheltered side of the dunes because large quantities of windblown detritus accumulate in these spaces. Their habitat choice is influenced by food supply. The slipfaces, although they occupy less than 1% of dune surfaces, are filled with insects and species endemic to the Namib Desert.^[2]

The toktokkie beetles have specific behaviors that allow them to survive in arid environments like the Namib Desert. Most of the beetles perform “headstands” to obtain moisture from the fog that rolls in from the Atlantic Ocean. Toktokkies time their movements around the fog, which usually rolls in during the late evening and early morning. The beetles will climb a dune and perform a “headstand” facing the west and collect fog on their entire body.^[2] Toktokkie beetles receive their name from a unique clicking noise they make. Their name is derived from the children's game where players knock on front doors and then run away. These beetles create this noise by raising and lowering their abdomen, like knocking, in quick sequences.^[4]