An exceptionally preserved 110 million years old praying mantis provides new insights into the predatory behaviour of early mantodeans

Patterns of morphological evolution in the raptorial appendages of praying mantises

Mantodea (praying mantises) is a group of exclusively predatory insects, which, together with nonraptorial blattodeans (cockroaches and termites) and groups exclusively found in the fossil record, form the group Dictyoptera. A central characteristic of Mantodea is the specialization of their first pair of legs as raptorial grasping appendages, but the evolution from walking to raptorial legs is not yet fully understood. Here, we trace the evolution of the raptorial appendages in Dictyoptera through time using a morphometric (morphospaces) approach. We also describe two new mantodean nymphs preserved in amber from the Cretaceous and Eocene, which expand the scarce mantodean fossil record. Blattodean and mantodean appendages appear distinct in morphospace, but several appendages of fossil non-mantodeans can be considered raptorial, providing a potential transitional link between walking and raptorial morphotypes. Therefore, we discuss potential mantodean affinities for other predatory fossil dictyopterans. We examine changes across extant mantodeans, characterized by a straightening of the tibia especially associated with the rise of the diversification of the Mantidea and discuss whether a thickening of the femur could reflect an early adaptation to cursorial hunting.

Functional morphology of the raptorial forelegs in Mantispa styriaca (Insecta: Neuroptera)

The insect leg is a multifunctional device, varying tremendously in form and function within Insecta: from a common walking leg, to burrowing, swimming or jumping devices, up to spinning apparatuses or tools for prey capturing. Raptorial forelegs, as predatory striking and grasping devices, represent a prominent example for convergent evolution within insects showing strong morphological and behavioural adaptations for a lifestyle as an ambush predator. However, apart from praying mantises (Mantodea)—the most prominent example of this lifestyle—the knowledge on morphology, anatomy, and the functionality of insect raptorial forelegs, in general, is scarce. Here, we show a detailed morphological description of raptorial forelegs of Mantispa styriaca (Neuroptera), including musculature and the material composition in their cuticle; further, we will discuss the mechanism of the predatory strike. We could confirm all 15 muscles previously described for mantis lacewings, regarding extrinsic and intrinsic musculature, expanding it for one important new muscle—M24c. Combining the information from all of our results, we were able to identify a possible catapult mechanism (latch-mediated spring actuation system) as a driving force of the predatory strike, never proposed for mantis lacewings before. Our results lead to a better understanding of the biomechanical aspects of the predatory strike in Mantispidae. This study further represents a starting point for a comprehensive biomechanical investigation of the convergently evolved raptorial forelegs in insects.

Cretaceous mantid lacewings with specialized raptorial forelegs illuminate modification of prey capture (Insecta: Neuroptera)

The Mantispidae (Neuroptera), commonly known as mantid lacewings or mantispids, are characterized by raptorial forelegs used by adults for predation. They have a fossil history extending to the Early Jurassic. During the past 180 Myr, the lineage has undergone significant evolutionary transformation, exhibiting an elevated diversity in morphology yet retaining the same overall ground plan. Although raptorial foreleg morphology and capture behaviour are well documented in extant insects, they are poorly known for premodern lineages, attributable to the scarcity and poor preservation of fossils. Here, we report two new genera and species of Mantispidae from mid-Cretaceous Myanmar (Burmese) amber. Both taxa have highly specialized raptorial forelegs and highlight modification of capture strategy in Cretaceous Mantispidae. The foreleg of both species has one major spine that is the same length as the foretibia on the ventral surface of the forefemur, which faces the foretibia with a row of robust setae. The two new amber mantid lacewings provide structural and functional indications that represent an extinct mode of capture strategy. The new findings reveal the presence of a geochronologically rapid diversification of Mantispidae during the Early Cretaceous, thereby illuminating the varied morphologies involved in prey-capture strategies integral to the early evolution of mantispids.

Cretaceous diversity and disparity in a lacewing lineage of predators (Neuroptera: Mantispidae)

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.

An unusual 100-million-year old holometabolan larva with a piercing mouth cone

Holometabola is a hyperdiverse group characterised by a strong morphological differentiation between early post-embryonic stages (= larvae) and adults. Adult forms of Holometabola, such as wasps, bees, beetles, butterflies, mosquitoes or flies, are strongly differentiated concerning their mouth parts. The larvae most often seem to retain rather plesiomorphic-appearing cutting-grinding mouth parts. Here we report a new unusual larva preserved in Burmese amber. Its mouth parts appear beak-like, forming a distinct piercing mouth cone. Such a morphology is extremely rare among larval forms, restricted to those of some beetles and lacewings. The mouth parts of the new fossil are forward oriented (prognathous). Additionally, the larva has distinct subdivisions of tergites and sternites into several sclerites. Also, the abdomen segments bear prominent protrusions. We discuss this unusual combination of characters in comparison to the many different types of holometabolan larvae. The here reported larva is a new addition to the 'unusual zoo' of the Cretaceous fauna including numerous, very unusual appearing forms that have gone extinct at the Cretaceous-Palaeogene boundary.

Response to "An exceptionally preserved 110 million years old praying mantis provides new insights into the predatory behaviour of early mantodeans"

Hörnig, Haug & Haug (2017) published a description of a new specimen of Santanmantis axelrodi MB.I.2068, an extinct species of praying mantis from the Crato Formation of Brazil. According to Hörnig, Haug & Haug (2017), the discovery of this new specimen brought with it implications for praying mantis character evolution and predatory behavior; it is with these lines of reasoning that we find fault. More specifically, we point to four flawed assumptions in their study that led to their unsubstantiated conclusion that S. axelrodi employed their mesothoracic legs in prey capture.