Hardened elytra of flightless desert darkling beetles act as effective armour against predators

Flightless invertebrates are highly exposed to predators and have evolved various defensive strategies. Although body hardening is a common physical defence in arthropods, the protective function of hardened elytra in insects remains insufficiently understood, particularly in the context of predator–prey interactions that occur under natural field conditions. We investigated whether the fused elytra of three flightless, nocturnal darkling beetles ( Pimelia senegalensis , P. angulata and Prionotheca coronata ) function as effective physical armour against predators in the Sahara Desert. Field observations were conducted to quantify injury frequencies as evidence of predator attacks. Behavioural assays were also performed using two natural predators, jerboas ( Jaculus jaculus ) and carabid beetles ( Anthia duodecimguttata ), to test predation success on intact and elytra‐removed beetles. Field surveys revealed that many individuals had lost one or more legs, indicating frequent predation attempts but suggesting that these beetles often survived such attacks. In behavioural trials, jerboas consumed smaller beetles but failed to feed on larger, spiny species. Similarly, carabid beetles rarely consumed intact beetles, whereas all elytra‐removed individuals were consumed. Because beetles with re‐attached elytra from which chemical factors had been removed were not consumed, chemical defences appear to play little or no role. These findings demonstrate that elytral sclerotisation in flightless darkling beetles functions as a morphological anti‐predator defence, effectively offsetting the disadvantages of flightlessness under intense predation pressure, although its effectiveness depends partly on predator size.