Mantidflies (Mantispidae) are an unusual and charismatic group of predatory lacewings (Neuroptera), whereby the adults represent a remarkable case of morphological and functional convergence with praying mantises (Mantodea). The evolutionary history of mantidflies remains largely unknown due to a scarcity of fossils. Here, we report the discovery of a highly diverse palaeofauna of mantidflies from the mid-Cretaceous (lowermost Cenomanian) of Myanmar. The raptorial forelegs of these mantidflies possess highly divergent morphological modifications, some of which are unknown among modern mantidflies, e.g. the presence of forked basal profemoral spines or even the complete loss of foreleg spine-like structures. A phylogenetic analysis of Mantispidae reveals a pattern of raptorial foreleg evolution across the family. The high species diversity and disparate foreleg characters might have been driven by diverse niches of predator–prey interplay in the complex tropical forest ecosystem of the mid-Cretaceous.

Mantispoidea (Insecta, Neuroptera) are well-known for the hypermetamorphic larval development and for most adults having praying mantis-like raptorial forelegs. Currently, this superfamily comprises Berothidae (beaded lacewings) and three raptorial mantispoid families: Rhachiberothidae (thorny lacewings), Dipteromantispidae and Mantispidae (mantidflies or mantid lacewings). It includes about 530 extant species in 74 genera, and 143 extinct species in 97 genera from the Upper Triassic to the Miocene. Berothidae, well-known for some adults with scale-like setae on the female wings, currently includes 119 extant species in 26 genera, and 59 extinct species in 37 genera from the Upper Triassic to the Eocene. Rhachiberothidae represents the relictual group of Mantispoidea, comprising only 14 extant species across four genera, which are confined to the Afrotropical Region. However, the abundant fossil records (28 species and 21 genera), especially from the Cretaceous, highlight the past glory of this family. The Cretaceous dipteran-like family Dipteromantispidae, comprising ten species across nine genera, remains enigmatic in terms of its phylogenetic status. Mantispidae, the largest family within Mantispoidea, comprises approximately 395 extant species across 44 genera and 46 extinct species in 30 genera, ranging from the Lower Jurassic to the Miocene. This family is distinctive from other raptorial families for its highly mobile and variously elongated prothorax. Here, we describe several new genera and species from mid-Cretaceous Kachin amber, Myanmar: Three new species of Osmyloberotha Khramov, 2021 (O. dispersa sp. nov., O. chenzuyini Zhuo, Li & Liu sp. nov. and O. magnimaculata sp. nov.) in Berothidae, with a detailed redescription of O. simpla Khramov, 2021; two new genera and three new species (Paraberothinae: Paraberothoides longispina Li, Zhang & Liu gen. et sp. nov.; Subfamily unknown: Dicranoberotha zhangzhiqiae Zhuo, Li & Liu gen. et sp. nov., Dicranoberotha liumohanae Zhuo, Li & Liu gen. et sp. nov.) of Rhachiberothidae, three new species (Enigmadipteromantispa dilatata Li, Nakamine, Yamamoto & Liu sp. nov., Kurtodipteromantispa relicta Li, Nakamine, Yamamoto & Liu sp. nov. and Kurtodipteromantispa univenula sp. nov.) of Dipteromantispidae, as well as four new genera and five new species (Symphrasinae: Parvosymphrasites aploneura Li, Lin, Liu & Wang gen. et sp. nov. and Proplega evelynae Zhuo, Li & Liu gen. et sp. nov.; Subfamily unknown: Haplacantha robusta gen. et sp. nov., Haplacantha tenuis gen. et sp. nov. and Mesomantispoides felixoporcus gen. et sp. nov.) of Mantispidae. Sinuijumantispa So & Won, 2022, previously classified within Drepanicinae, is now recognized as a stem group of Mantispidae, which is possibly related to Mesomantispoides gen. nov. or Mesomantispinae. Our new findings offer crucial insights into the taxonomy, morphological diversity and evolution of Mantispoidea.