Suspended resting of caterpillars as an anti-predator strategy

Resting animals are highly vulnerable to predation, making the location and manner in which they rest crucial for their survival. Some lepidopteran larvae and spiders rest while suspended in the air at night. Although previous studies have hypothesised that nocturnal suspended resting serves as an anti-predator defence, this hypothesis has not yet been tested. We found that Pogonopygia nigralbata larvae (Lepidoptera: Geometridae: Ennominae) rest on leaves of the host plant Illicium anisatum (Austrobaileyales: Schisandraceae) during the day but hang from leaves by a thread at night. As some predators, such as praying mantises, centipedes and tree frogs, were observed on host plants at night, the larvae might hang from leaves to avoid encounters with these predators. To test this hypothesis, we artificially placed model prey (i.e., live mealworms) on I. anisatum trees during the day and at night. We compared the attack rates on model prey suspended from leaves with those directly attached to the leaves. Model prey were attacked more frequently during the day than at night. Suspended models were attacked less frequently than those attached leaves at night. A mealworm attached to a leaf was also consumed by a centipede at night. Additionally, centipedes were found more frequently on the host plant I. anisatum at night than during the day. Furthermore, our laboratory experiments showed that P. nigralbata larvae were frequently consumed by praying mantises and centipedes. Our results suggest that the nocturnal suspended resting of P. nigralbata larvae plays a crucial role in evading nocturnal predators, such as praying mantises and centipedes. We found that Pogonopygia nigralbata larvae rest on the leaves of I. anisatum during the day but hang by a thread at night. Some predators, such as praying mantises, centipedes and tree frogs, were frequently observed on the host plants at night. Our field observations and experiments suggest that the nocturnal suspended resting of P. nigralbata larvae plays a crucial role in evading nocturnal predators, such as praying mantises and centipedes. image