Sandy pitfall traps of antlions are elaborate constructions to capture prey. Antlions exploit the interactions between the particles in their habitat and build a stable trap. This trap is close to the unstable state; prey items will slide towards the centre—where the antlion ambushes—when entering the trap. This is efficient but requires permanent maintenance. According to the present knowledge, antlions throw sand, mainly to cause sandslides towards the centre of the pit. We hypothesized that: (i) sand-throwing causes sandslides towards the centre of the pit and (ii) sand-throwing constantly maintains the pitfall trap and thus keeps its efficiency high. Using laboratory experiments, as well as finite-element analysis, we tested these hypotheses. We show, experimentally and numerically, that sand that accumulates at the centre of the pit will be removed continuously by sand-throwing, this maintenance is leading to slope condition close to an unstable state. This keeps the slope angle steep and the efficiency of the trap constant. Furthermore, the resulting sandslides can relocate the trapped prey towards the centre of the pit. This study adds further insights from specific mechanical properties of a granular medium into the behavioural context of hunting antlion larvae.

蚁狮的沙质陷阱是捕捉猎物的精心构造。蚁狮利用其栖息地中粒子之间的相互作用并建立一个稳定的陷阱。这个陷阱接近于不稳定状态；进入陷阱时，猎物会滑向蚁狮伏击的中心。这是有效的，但需要永久维护。据目前所知，蚁狮抛沙，主要是造成向坑中心方向滑坡。我们假设：（i）抛沙导致向坑中心滑坡，（ii）抛沙不断维持陷阱陷阱，从而保持其高效率。通过实验室实验以及有限元分析，我们检验了这些假设。我们通过实验和数值证明，堆积在坑中心的沙子将通过抛沙不断被清除，这种维护导致边坡状况接近不稳定状态。这使倾斜角保持陡峭，并且陷阱的效率保持不变。此外，由此产生的滑坡可以将被困的猎物重新定位到坑的中心。这项研究将粒状介质的特定机械特性的进一步见解添加到狩猎蚁狮幼虫的行为背景中。