Selection for predation, not female fecundity, explains sexual size dimorphism in the orchid mantises

Coloration in a Praying Mantis: Color Change, Sexual Color Dimorphism, and Possible Camouflage Strategies

Background matching, an important form of camouflage, can be challenging for animals that range across heterogeneously colored habitats. To remain cryptic in such habitats, animals may employ color change, background choice, or generalist coloration, and the efficacy of these strategies may be influenced by an animal's mobility. We examined camouflage strategies in the praying mantis Stagmomantis limbata. We reared mantids in green or brown containers to test whether mantids change color over development to match their background. Additionally, we tested whether adult mantids (i) employ behavioral background choice, (ii) exhibit sexual color dimorphism, and (iii) differ in mobility in the field. Mantids changed color during development in response to their background, but the effect was small and variable. Adult mantids did not show background choice. In the field, adult males moved greater distances than females. Adults exhibited sexual color dimorphism: Males were heterogeneous in coloration (green body with brown pronotum), while females were more homogeneous in color, ranging continuously from green to brown. We suggest a hypothesis that differences in mobility between the sexes have led to the sexual color dimorphism observed and that this dimorphism reflects different camouflage strategies, with highly mobile males showing a generalist coloration and more sedentary females showing a specialist coloration.

Foraging strategy as a route for sexual size dimorphism evolution

Female-biased sexual size dimorphism stands as a widespread evolutionary pattern. Fecundity selection, favouring larger females with greater reproductive output, is a leading explanation. However, larger body sizes demand greater energy intake, potentially hindering the evolution of extreme female sizes. Thus, the evolution of more lucrative foraging tactics may allow for an increase in size. Hence, coupled with selection against larger males, fecundity selection should result in larger SSD in species with more lucrative foraging strategies. Crab spiders are sit-and-wait predators that hunt in several plant substrata. Species that forage on flowers or employ prey-luring strategies likely have access to higher food intake than other species. We extracted body size measurements of 614 crab spider species from 43 genera and classified them based on their foraging strategy. Our findings show that foraging strategies that provide higher energy input (EFS) result in larger SSD. Statistical estimates indicate that females have a cephalothorax width 91% larger than males in EFS species, compared to 26% larger females than males in non-EFS species. These differences possibly arise due to larger females and smaller males. The effects on male size reduction might result from scramble competition, whereas the increase in female size is likely due to fecundity selection. These results suggest that the shift towards more lucrative foraging strategies may have been a key event in body size and SSD evolution in crab spiders.

First Record of Creobroter apicalis Saussure, 1869 (Mantodea: Hymenopodidae) in the Southern Province of Sri Lanka: Unveiling a New Geographic Record of Flower Mantis

In Sri Lanka, the genus Creobroter has received inadequate attention, resulting in a scarcity of information with only C. pictipennis being recorded. We report the presence of Creobroter apicalis in Sri Lanka for the first time, extending its geographic distribution to Matara District, Southern Sri Lanka. Species identification was made with an examination of adult male and female specimens for morphological characters through detailed examination and reference to available literature and keys. Identification was confirmed with molecular analysis and comparison with other sequenced Creobroter spp.

Evolutionary genomics of camouflage innovation in the orchid mantis

The orchid mantises achieve camouflage with morphological modifications in body color and pattern, providing an interesting model for understanding phenotypic innovation. However, a reference genome is lacking for the order Mantodea. To unveil the mechanisms of plant-mimicking body coloration and patterns, we performed de novo assembly of two chromosome-level genomes of the orchid mantis and its close relative, the dead leaf mantis. Comparative genomic analysis revealed that the Scarlet gene plays an important role in the synthesis of xanthommatin, an important pigment for mantis camouflage coloration. Combining developmental transcriptomic analysis and genetic engineering experiments, we found that the cuticle was an essential component of the 'petal-like' enlargement, and specific expression in the ventral femur was controlled by Wnt signaling. The prolonged expression of Ultrabithorax (Ubx) accompanied by femoral expansion suggested that Ubx determines leg remodeling in the early developmental stage. We also found evidence of evolution of the Trypsin gene family for insectivory adaptation and ecdysone-dependent sexual dimorphism in body size. Overall, our study presents new genome catalogs and reveals the genetic and evolutionary mechanisms underlying the unique camouflage of the praying mantis, providing evolutionary developmental insights into phenotypic innovation and adaptation.

Extrinsic and intrinsic musculature of the raptorial forelegs in Mantodea (Insecta) in the light of functionality and sexual dimorphism

Prehensile raptorial forelegs are prey capturing and grasping devices, best known for praying mantises (Mantodea) within insects. They show strong morphological and behavioral adaptations toward a lifestyle as generalist arthropod predators. In the past, few species of Mantodea were investigated, concerning morphological variability of the raptorial forelegs. Especially the knowledge of foreleg anatomy in the light of functional and comparative morphology is scarce. Our comparative approach is based on the, for arthropods very common, "female-biased sexual size dimorphism" (SSD) that occurs in almost every Mantodea species. Within Mantodea, this SSD is likely leading to a shift of the exploited ecological niche between male and female individuals due to changes in, for example, the possible prey size; which might be reflected in the chosen ecomorphs. In this context, we analyzed the musculature of the raptorial forelegs of female and male specimens in five different species with varying SSD, using high-resolution microcomputed tomography and dissection. We were able to confirm the presence of 15 extrinsic and 15 intrinsic muscles-including one previously undescribed muscle present in all species. Thus, presenting a detailed description and illustrative three-dimensional anatomical visualization of the musculature in Mantodea. Interestingly, almost no observable differences were found, neither between species, nor between the sexes. Furthermore, we homologized all described muscles, due to their attachment points, to the comprehensive nomenclature established by Friedrich and Beutel (2008), discussed potential functionality of the muscles and possible homologies to the neuropteran Mantispa styriaca (Büsse et al., 2021) and the newly introduced leg nomenclature by Aibekova et al. (2022). By elucidating the anatomy, particularly in the context of functionality and SSD, our results complement previous knowledge of the raptorial forelegs, and facilitate a better understanding of the underlying biomechanical system of the predatory strike, and ultimately, a future comparison to other insect taxa.

Variations in the carapace shape of whip spiders (Arachnida: Amblypygi)

Morphological studies often need to reference body size to correctly characterise the shape of organisms. In arthropods, the most commonly used reference for this is the length or width of the carapace, thorax, or the prosoma in the case of chelicerates. However, in the case of animals with unlimited growth, such as whip spiders, this measure could be irrelevant if growth is allometric. In this study, we analyse the ontogenetic modifications in prosoma outline shape in whip spiders during growth and compare the differences in shape between species. Differences are important for the relative prosoma width between species and, in the case of Damon medius, during growth in the juvenile stages, whereas the shape remains stable in mature stages. We conclude that a one-dimensional measure (i.e., length or width) suffices for mature specimens of a single species or family, but for larger studies, or when including immature specimens, at least the prosoma area (within the outline shape) should be used as a size estimator.

Context dependent effects on attack and defense behaviors in the praying mantis Tenodera sinensis

Most behavior needs to strike a balance between the competing needs to find food and protect an animal from predators. The factors that influence this balance and the resulting behavior are not well understood in many animals. Here we examined these influences in the praying mantis Tenodera sinensis (Saussure) by presenting perching individuals with alternating sinusoidally moving prey-like stimuli and rapidly expanding looming stimuli then scoring their behavior on a defensive - aggressive scale. In this way, we tested the hypothesis that such behaviors are highly context dependent. Specifically, we found that defensive responses, which are normally very consistent, are decreased in magnitude if the animal has just performed an aggressive response to the previous sinusoid. A thrash behavior not normally seen with looming alone was often seen following aggression. In thrashing the animal tries to push the looming stimulus away. It almost exclusively followed aggressive responses to the sinusoid stimulus. Moreover, aggression levels were found to shift from low to high and back to low as adult animals aged and, in general, female mantises were more aggressive than males. Finally, the specific nature of the mid-life spike in aggressive behaviors differed according to whether the animals were lab-raised or caught in the wild. Lab raised animals showed roughly equal amounts of increased attention to the stimulus and very aggressive strike behaviors whereas wild caught animals tended to either ignore the stimulus or react very aggressively with strikes. Therefore, our hypothesis regarding context dependent effects was supported with all 4 factors influencing the behaviors that were studied.

The evolution of startle displays: a case study in praying mantises

Anti-predator defences are typically regarded as relatively static signals that conceal prey or advertise their unprofitability. However, startle displays are complex performances that deter or confuse predators and can include a spectacular array of movements, colours and sounds. Yet, we do not fully understand the mechanisms by which they function, their evolutionary correlates, or the conditions under which they are performed and evolve. Here, we present, to our knowledge, the first phylogenetically controlled comparative analyses of startle displays including behavioural data, using praying mantises as a model system. We included 58 species that provide a good representation of mantis diversity and estimated the strength of phylogenetic signal in the presence and complexity of displays. We also tested hypotheses on potential evolutionary correlates, including primary defences and body size. We found that startle displays and morphological traits were phylogenetically conserved, whereas behavioural traits were highly labile. Surprisingly, body size was not correlated with display presence or complexity in phylogenetically controlled analyses. Species-rich clades were more likely to exhibit displays, suggesting that startle displays were probably involved in lineage diversification. We suggest that to further elucidate the conditions under which startle displays evolve, future work should include quantitative descriptions of multiple display components, habitat type, and predator communities. Understanding the evolution of startle displays is critical to our overall understanding of the theory behind predator-prey dynamics.

Evolutionary diversification in the raptorial forelegs of Mantodea: Relations to body size and depth perception

Limb proportions have evolved among animals to meet functional demands among diverse environments. Studies from terrestrial, vertebrate locomotion have demonstrated that variation in limb proportions have adaptively evolved so animals can perform in a given environment. Most of the research on limb proportion evolution is among vertebrates and terrestrial locomotion, with little information on limb segment evolution in invertebrates or for other functional roles. For example, among invertebrates, multisegmented raptorial forelimbs have evolved multiple times independently to capture prey, but there is little information on the adaptive evolution and diversity of these limbs. Furthermore, as feeding performance is influenced by the sensory system, few studies have examined the coevolution of sensory-motor systems. Using mantises (Mantodea) I examined forelimb diversification among 97 species with a combination of methods, including ternary plots for morphospace visualization, phylogenetically informed allometric relationships, and comparison of evolutionary rates of diversification. Furthermore, using head width as a proxy for depth perception, I examined the correlated evolution of foreleg diversity with depth perception. The results show that among the three segments of the foreleg, the tibia is the smallest, most diverse, and has the highest rate of evolution after body size corrections. Furthermore, while all foreleg segments were related to head width, head width explained the most variation in tibial length compared with other foreleg segments. The results suggest a potential adaptive functional role of tibia length related to the displacement or force produced in this mechanical lever. Furthermore, results from this study support distinct ecomorphs of mantises, as several independent evolutions to grass mimicry evolve similar morphologies. RESEARCH HIGHLIGHT: This study demonstrates interspecific variation among segments of an invertebrate raptorial foreleg. Among Mantodea species the tibia is the most diverse and is related to a proxy for depth perception, while the other segments had strong relationships with body size. This suggests an adaptive, functional role of the tibia during prey capture.

A novel form of wasp mimicry in a new species of praying mantis from the Amazon rainforest, Vespamantoida wherleyi gen. nov. sp. nov. (Mantodea, Mantoididae)

A wasp mimicking praying mantis (Mantodea) of the early evolving Mantoididae family was discovered in 2013 at a research station near the Amazon River in Northern Peru. This adult specimen exhibited a striking bright red/orange and black coloration pattern that was undocumented in all known praying mantis species. We tested the status of this new specimen using external morphology, male genital dissections, and geographic distribution. Our findings demonstrate the specimen to represent a new species, Vespamantoida wherleyi gen. nov. sp. nov., that is closely allied with a recently described species, Mantoida toulgoeti Roy, 2010, both of which are included within the newly erected genus. To support our actions, we present high resolution images of museum preserved and living specimens, morphological illustrations, a generic-level distribution map, and recorded video of the behavior of the holotype taken in the field at the time of collection. The bright red/orange coloration contrasted with black markings, the general appearance of a hymenopteran that includes a narrowed wasp waist, and the locomotory patterns and antennal movements mark this newly discovered species as unique among all hymenopteran mimicking Mantoididae as well as all other praying mantises.

Feeding ecology and sexual dimorphism in a speciose flower beetle clade (Hopliini: Scarabaeidae)

The relationship between feeding ecology and sexual dimorphism is examined in a speciose South African monkey beetle clade. We test whether feeding and mating at a fixed site (embedding guild) is associated with greater levels of sexual dimorphism and possibly sexual selection than species using unpredictable feeding resources (non-embedding guild). Sexual dimorphism was measured using a point scoring system for hind leg and colour across the two feeding guilds for >50% of the regional fauna. Quantification of hind leg dimorphism using a scoring system and allometric scaling were used to identify traits subject to sexual selection. Feeding guild had a significant effect on hind leg dimorphism, with embedders having high and non-embedders low scores. The sessile and defendable distribution of females on stable platform flowers may favour contests and associated hind leg weaponry. In contrast, degree of colour dimorphism between the sexes was not associated with any particular feeding guild, and may serve to reduce male conflict and combat. Embedder males had high proportions (∼76%) of species with positive allometric slopes for almost all hind leg traits. For male non-embedders, only ∼37% of species showed positive scaling relationships. Phylogenetic data, in conjunction with behavioural data on the function of leg weaponry and visual signalling among males is needed to better understand the link between sexual dimorphism and sexual selection in the radiation of the monkey beetles.

An elusive Neotropical giant, Hondurantemna chespiritoi gen. n. & sp. n. (Antemninae, Mantidae): a new lineage of mantises exhibiting an ontogenetic change in cryptic strategy

We present the description of a new genus and new species of praying mantis, Hondurantemna chespiritoigen. n. & sp. n. This species of cryptic mantis, collected in National parks in Mexico and Honduras, remained unknown despite its considerable body size. Based on a phylogenetic analysis with molecular data and traditional morphological analysis, we place this new genus within Antemninae, a monotypic Mantidae subfamily. We update the subfamily concept for Antemninae and provide a key to the two genera. We describe the external morphology of immatures and adults of the new species as well as the genital complexes of both sexes and the ootheca of Antemna rapax. The observed morphological changes between immature and adult females suggests that the selection for an alternate strategy for crypsis is a response to size increase of the abdomen during development. Immatures exploit a stick/branch habitat based on their morphological appearance while adult females appear as a leaf to disguise the profile of the body.