A mantidfly in Cretaceous Spanish amber provides insights into the evolution of integumentary specialisations on the raptorial foreleg

Ricardo Pérez-De La Fuente,Enrique Peñalver

doi:10.1038/s41598-019-49398-1

Ricardo Pérez-De La Fuente, Enrique Peñalver

Open Access

https://doi.org/10.1038/s41598-019-49398-1

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Abstract

Multiple predatory insect lineages have developed a raptorial lifestyle by which they strike and hold prey using modified forelegs armed with spine-like structures and other integumentary specialisations. However, how structures enabling the raptorial function evolved in insects remains largely hypothetical or inferred through phylogeny due to the rarity of meaningful fossils. This is particularly true for mantidflies (Neuroptera: Mantispidae), which have a scarce fossil record mostly based on rock compressions, namely isolated wings. Here, Aragomantispa lacerata gen. et sp. nov. is described from ca. 105-million-year-old San Just amber (Spain), representing the oldest and one of the few mantidflies hitherto described from amber. The fossil shows exquisitely preserved forefemoral spine-like structures composed of integumentary processes each bearing a modified seta, and prostrate setae on foretibiae and foretarsi. The fine morphology of these structures was unknown in fossil mantidflies. An assessment of integumentary specialisations from raptorial forelegs across mantispoid lacewings is provided. The present finding reveals how the specialised foreleg armature associated to the raptorial lifestyle in extant mantidflies was present yet not fully established by the Early Cretaceous, at least in some lineages, and provides palaeontological evidence supporting certain evolutionary patterns of acquisition of integumentary specialisations related to the raptorial function in the group.

Highlights

Among predatory insects, various lineages swiftly strike and hold prey using modified forelegs armed with diverse specialised structures derived from the leg integument, such as spine-like bristles
Other fossil species assigned to Mantispidae described from compressions correspond to wings, mostly isolated, i.e., three Mesozoic species affiliated to Drepanicinae[32,33,34], one Eocene species assigned to Symphrasinae[29], and three Oligocene species classified in Mantispinae[35,36,37]
We present a fossil mantidfly with exquisitely preserved integumentary specialisations on the raptorial forelegs, including prostrate setae and spine-like structures composed of integumentary processes each bearing a modified seta

Summary

Introduction

Various lineages swiftly strike and hold prey using modified forelegs armed with diverse specialised structures derived from the leg integument, such as spine-like bristles (setae) In extant insects, these specialised, raptorial forelegs are most famously distinctive of praying mantises[1], but are present in some aquatic hemipterans[2], some assassin bugs[3], some true flies[4,5,6], a few beetles[7], and mantidflies. We present a fossil mantidfly with exquisitely preserved integumentary specialisations on the raptorial forelegs, including prostrate setae and spine-like structures composed of integumentary processes each bearing a modified seta. Some evolutionary trends of integumentary specialisations related to the raptorial lifestyle in insects have been inferred phylogenetically[1,2,52], the fossil record able to contribute to the subject is scarce and was hitherto restricted to praying mantises[1,53]

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