Widespread mimicry and camouflage among mid-Cretaceous insects

Abstract

The avoidance of detection by predators and parasites is critical to survival. Two complex mechanisms for such avoidance are mimicry and camouflage, with fossils providing valuable insight into the evolution of these strategies. Such fossil evidence is, however, rare, and the frequent partial and lopsided occurrence. Here, we report a diverse insect assemblage exhibiting these adaptations from mid-Cretaceous Kachin amber (99 million years ago), including plant mimesis in Tridactylidae (pygmy mole crickets) and debris-carrying camouflage in Gelastocoridae (toad bugs) and Psocodea (bark lice). Critically, Mesozoic plant mimesis in Tridactylidae is supported by our Siamese Network analysis, a Deep Learning model and potentially powerful tool for investigating ancient mimicry. Together with previously known records, our fossils demonstrate that most extant debris-carrying insects (eight groups with direct camouflage) had evolved exogenous camouflage by the mid-Cretaceous. Our results suggest that a complex biological response was already widespread among insects in mid-Cretaceous ecosystems during the rise of angiosperms, probably in response to similar selective pressures as experienced by their extant counterparts.