DOI: 10.5061/dryad.3xsj3txq1
title: Turning lances into shields: Flower mantids stretch their raptorial forelegs to avert and deflect predator attack

description: Evolutionary co-option, in which existing traits acquire novel adaptive
 functions, is a key strategy by which organisms adapt to new environmental
 challenges. Although such co-option has been widely documented at the
 genetic and morphological levels, its incidence at the behavioural level
 remains largely unknown. Mantids stretch their forelegs to capture prey;
 however, some flower mantids also perform foreleg stretches in the absence
 of prey. The current study tested whether this behaviour represents a
 novel function of the foreleg stretch, thus representing a case of
 behavioural co-option. Predator encounter behaviour assays revealed that
 foreleg stretching facilitates the escape of flower mantids from large
 predatory mantids by delaying predator approach or deflecting their attack
 towards less vulnerable body parts. Phylogenetic analysis suggested that
 the ancestral function of foreleg stretching involves prey capture, with
 the anti-predator function subsequently acquired in the flower mantid
 clade, coinciding with the diversification of large-sized mantids, the
 most likely invertebrate predators of flower mantids. This study provides
 a case of behavioural co-option, where a predator uses its predatory organ
 as a defensive implement to cope with its own predators. These findings
 further suggest that behavioural co-option may be common in nature,
 meriting more comprehensive studies.
description: <strong>Predator encounter
 assay</strong>   We
 performed predator encounter assays using 4th instar nymphs of the flower
 mantid <em>Astyliasula basinigra </em>(n = 26) as the model
 and 4th instar nymphs of the large-sized mantid Rhombodera longa (n = 9)
 as the predator.Results showed that:  
 (1) Foreleg stretching behaviour enhanced the survivor
 possibility of the flower mantids under predation risk.
   (2) Foreleg stretching can
 significantly delay and reduce predator attacks, likely by intimidating
 the predators or confusing predatory mantids regarding the target
 location.   (3) Foreleg
 stretching can deflect predators’ attacks from the more vulnerable body
 trunk to the less vulnerable forelegs, thereby facilitating escape after
 the attack.  
 <strong>Characterising the types of foreleg stretching
 behaviours</strong>  
 We compared the stretching behaviour among three flower mantid
 species: <em>A. basinigra, Pseudocreobotra wahlbergii</em>,
 and <em>Acromantis hesione</em>. Type I is characterised by
 the alternative extension of both forelegs to opposite sides of the body
 axis, with each leg extending at a large angle relative to the body’s
 central axis (approximately 56.90°). This mode is often accompanied by the
 shivering of the tibia and tarsus. Type II is the simplest of the three
 types, involving simultaneous forward stretching of both forelegs at a
 much smaller angle (approximately 2.83°) to the body’s central axis,
 making the inner surfaces of the forelegs concealed and resembling the
 predatory strike behaviour during hunting. Type III involves the
 alternative extension and withdrawal of the forelegs in a circling motion,
 with the angle of stretching falling between that of type I and type II
 (approximately 21.99°).  
 <strong>Morphometrics of foreleg
 femurs</strong>   We
 selected 16 adult <em>A. basinigra</em> specimens (n = 8 for
 each sex) to measure the morphology of foreleg femurs. The length, width
 and thickness of the femurs were measured using a digital calliper. The
 right foreleg femur of each specimen was measured. Additionally, to
 reflect the variation in foreleg femur extension among flower mantids, we
 selected 93 specimens from 7 species which exhibiting 4 distinct foreleg
 stretching patterns (Type I, Type II, Type I+II, and Type III). The
 relative width (width/length) of the femur was measured for these
 specimens. Result revealed that at the early stage of the evolution of
 stretching behaviour, with the emergence of the type II behaviour,
 lineages exhibiting stretching behaviour showed almost no femur expansion.
 Greater femur expansion appeared following the evolution of the more
 derived stretching behaviour types, types I and III.
   <strong>Frequency measurement of
 behaviour</strong>  
 To determine whether foreleg stretching behaviour occurs more
 frequently during moving in <em>A. basinigra</em> flower
 mantids, we selected seven 3rd instar individuals with similar moulting
 times. To account for the diurnal activity of mantids, video recording
 began at 8:00 AM and lasted for 12 hours. The experiment lasted for seven
 days. Result showed that foreleg stretching behaviour is frequently
 exhibited even when flower mantids are actively moving, a state in which
 they are more likely to be detected by ambushing predators. In contrast,
 flower mantids barely stretch their forelegs when at rest.
   <strong>Speed comparison between
 control and treatment group</strong>
   To assess whether our manipulation
 affected the movement speed of mantids, potentially influencing their
 survival under predation, we compared the mean speeds of individuals from
 the control (normal) group and the treatment (forelegs-disabled) group.
 Result showed that there is no significant difference between the two
 groups.  
 <strong>Taxon sampling and phylogenetic
 analyses</strong>   We
 utilized mitogenomes and nuclear DNA from a curated taxon set of 50 mantid
 species to reconstruct their phylogenetic relationships. By employing
 advanced mitochondrial phylogenomic workflow and ancestral state
 reconstruction, our results obtained the phylogenetic tree with high
 support value, with its topology aligning with widely accepted hypotheses
 of evolutionary relationships of Hymenopodidae.
   <strong>Divergence time
 estimation and ancestral state reconstruction</strong>
   To better understand the evolutionary
 trajectory and temporal rates of change in foreleg stretching behaviors,
 we conducted ancestral state reconstructions and rate estimations of
 character transitions using the phylogenetic relationships and foreleg
 stretching behavioral datasets we established for various mantodean
 species. Our analysis, facilitated by functions in the phytools package,
 suggested that the ancestral function of foreleg stretching was associated
 with prey capture. This function later evolved to incorporate
 anti-predator mechanisms within the flower mantid clade, aligning with the
 diversification of large-sized mantids, which are likely the primary
 invertebrate predators of these flower mantids.
description: # Turning the lances into the shield: Flower mantids stretch raptorial
 forelegs to avert and deflect predator attack
 [https://doi.org/10.5061/dryad.3xsj3txq1](https://doi.org/10.5061/dryad.3xsj3txq1) Contact Yuanlang Li ([lyls71120@163.com](mailto:lyls71120@163.com)) with any questions. This manuscript has been accepted for publication at Proceedings of Royal Society B. Li Y, Liu Q, Chen Z, Liang L, Wang Z, Duan Y, Song F, Cai W, Ge J, Li H, Tian L. Turning lances into shields: flower mantids stretch their raptorial forelegs to avert and deflect predator attack. *Proc. R. Soc. B* (accepted). 10.1098/rspb.2024.3081 ## Description of the data and file structure ### Files and variables #### File: DataS1.csv **Description:** Data from *Predator encounter assay*, including normal groups and manipulated group. ##### Variables * Predator IDs: Predator identity number * Flower mantid IDs: Flower mantid identity number * If stretching: Flower mantid stretching or not * Targets: Predator’s targets * Outcomes: Outcomes of the Predator encounter assay * Treatments: Control or Forelegs-disabled #### File: DataS2.csv **Description:** Data from *Predator encounter assay*, showing deviation angles of predators’ head before and after foreleg stretching. ##### Variables * Before : Deviation angles (deg) of predators’ head before foreleg stretching * After : Deviation angles (deg) of predators’ head after foreleg stretching #### File: DataS3.csv **Description:** Data from *Predator encounter assay*, showing predators’ speed when they are approaching the flower mantids. ##### Variables * Event IDs: Event identity number * Time since prey detection (sec): Time since prey detection * Distance (mm): Distance between predator and flower mantid #### File: DataS4.csv **Description:** Data from *Characterising the types of foreleg stretching behaviours*. ##### Variables * Behaviour IDs: Behaviour type’s identity number * Point IDs: Point identity number * x (mm): X-axis coordinate * y (mm): Y-axis coordinate #### File: DataS5.csv **Description:** Data from *Morphometrics of foreleg femurs*, including the morphological data of foreleg-femurs of 16 adult *A.* *basinigra *specimens. ##### Variables * Specimen IDs: Specimen identity number * Sex: Sex of specimen * Length (mm): Length of foreleg-femurs * Width (mm): Width of foreleg-femurs * Thickness (mm): Thickness of foreleg-femurs #### File: DataS6.csv **Description:** Data from *Morphometrics of foreleg femurs*, including the morphological data of foreleg-femurs of selected 93 specimens from 7 Hymenopodidae species. ##### Variables * Species: Scientific names of selected Hymenopodidae species * Specimen IDs: Specimen identity number * Sex: Sex of specimen * Femur length (mm): Length of foreleg-femurs * Femur width (mm): Width of foreleg-femurs * Relative width: Femur width/Femur length (dimensionless number) #### File: DataS7.csv **Description:** Data from *Frequency measurement of behaviour*. ##### Variables * Resting: Stretching times per minute when mantid in ‘resting’ * Moving: Stretching times per minute when mantid in ‘moving’ #### File: DataS8.csv **Description:** Data from *Speed comparison between control and treatment group*. ##### Variables * Mean.speed.CK: Mean speed (mm/s) of control group - Mean.speed.TR: Mean speed (mm/s) of treatment group #### File: glmm.data.xlsx **Description:** Data for GLMMs, original record see DataS1.csv. ##### Variables: * predator_id: Predator identity number * prey_id: Flower mantid identity number * experience: The number of encounters of predator with flower mantid * prey_stretching: Flower mantid stretching or not ("1", stretching; "0", non stretching) * escape: Experiment outcome ("1", Escape; "0", Capture) #### File: Chisq.test.data.txt **Description:** Data for chisq-test, original record see DataS1.csv. #### File: linear.regression.data.txt **Description:** Data for linear regression, original record see DataS3.csv. ##### Variables: * Stretching: Stretching or not ("1", non stretching; "2", stretching) - Time: Time since prey detection (sec) * Distance: Distance between predator and flower mantid (mm) #### File: DNA\_Information.pdf **Description:** DNA sequences information ##### Information: * Species: Scientific names of species * Accession number: NCBI number - Collection information: Collection information of specimens #### File: Mantidea\_state\_matrix.csv **Description:** Data for phylogenetic analyses. ##### Information: * Species: Scientific names of selected Hymenopodidae species * x: Behavioural state #### File: hymenopodidae\_Mantidae.csv **Description:** Supporting file for *Species_Distribution_and_Point_Data* **Information:** * Longitude: Longitude position * Latitude: Latitude position * family: Taxonomic rank ("Mantidae" or "Hymenopodidae") ## Codes information The following four files include the R codes used in this article. For more detailed information, please refer to our code annotations, main text, and supplemental materials (DOI: 10.1098/rspb.2024.3081). R Studio software, v. 2024.09.1+394, R software, v. 4.2.2 (R Core Team, 2024) ### Statistical.Codes R codes for statistical analysis. Including: (1) regarding GLMMs and Chisq-tests for *Predator encounter assay* (Based on DataS1); (2) t-test for *Frequency measurement of behaviour* (Based on DataS7); (3) t-test for *Deviation angle of predator's head* (Based on DataS2); (4) t-test for *Speed comparison between control and treatment group* (Based on DataS8); (5) linear regression for *The change in relative distance between predators and flower mantids over time* (Based on DataS3). ### Reconstruction\_of\_Ancestral\_States\_and\_rate\_change\_across\_time R codes for *Divergence time estimation and ancestral state reconstruction*. ### Mantidea\_pruned\_outgroups.tree Phylogenetic tree file. ### Species\_Distribution\_and\_Point\_Data R codes for generating species distribution maps (see Figure S1). ## Version changes **5-Mar-2025:**  (1) Provided new data files (including glmm.data.xlsx, Chisq.test.data.pdf, and linear.regression.data.txt) for statistical analyses. (2) Revised DataS2, DataS7, and DataS8 for statistical analyses. The changes only involve formatting and column names to facilitate statistical analyses; the original data remains unchanged. (3) Provided supporting file (hymenopodidae_Mantidae.csv, and Mantidea_state_matrix.csv) for statistical analysis. Please note that this version does not modify any of the original data.