DOI: 10.5061/dryad.b2rbnzsbm
title: Data for: Pendulum-based measurements reveal impact dynamics at the scale of a trap-jaw ant

description: Small organisms can produce powerful, sub-millisecond impacts by moving
 tiny structures at high accelerations. We developed and validated a
 pendulum device to measure the impact energetics of microgram-sized
 trap-jaw ant mandibles accelerated against targets at 105 m s-2. Trap-jaw
 ants (Odontomachus brunneus; 19 individuals; 212 strikes) were suspended
 on one pendulum and struck swappable targets that were either attached to
 an opposing pendulum or fixed in place. Mean post-impact kinetic energy
 (energy from strike converted to pendulum motion) was higher with a stiff
 target (21.0-21.5 µJ) than a compliant target (6.4-6.5 µJ). Target
 mobility had relatively little influence. Mean contact duration of strikes
 against stiff targets was shorter (3.9-4.5 ms) than against compliant
 targets (6.2-7.9 ms). Shorter contact duration was correlated with higher
 post-impact kinetic energy. These findings contextualize and provide an
 energetic explanation for the diverse, natural uses of trap-jaw ant
 strikes such as impaling prey, launching away threats, and performing
 mandible-powered jumps. The strong effect of target material on energetic
 exchange suggests material interactions as an avenue for tuning
 performance of small, high acceleration impacts. Our device offers a
 foundation for novel research into the ecomechanics and evolution of tiny
 biological impacts and their application in synthetic systems.
description: <strong>Tracks: </strong><em>tracks.zip</em> These are the outputs from the automated digitizing routine. Each file has the A#**#.csv naming scheme where the A# stands for the ant number, the ** specifies the target type (C = Compliant, S = Stiff, FC = Fixed Compliant, FS = Fixed Stiff), and the last # represents the strike number. In each file, the column titles are as follows: pt1_cam1_X: The x coordinates for the ant pendulum immediately after impact<br> pt1_cam1_Y: The y coordinates for the ant pendulum immediately after impact<br> pt2_cam2_X: The x coordinates for the target pendulum immediately after impact (note that this column does not exist for the fixed targets as the target does not move after impact)<br> pt2_cam2_Y: The y coordinates for the target pendulum immediately after impact (note that this column does not exist for the fixed targets as the target does not move after impact) <strong>Verification impactor dataset:</strong> <em>mICP_Impactor_Dataset.csv</em> This contains the dataset of impacts with the verification impactor as the energy source. Information included is as follows: group: Specifies the target type where C = Compliant, S = Stiff, FC = Fixed Compliant, and FS = Fixed Steel   <br> strike: Strike number - specifies the order of the observation in the amount of strikes performed by the ant for this target type  <br> initial: The amount of energy delivered by the swinging impactor pendulum measured in Joules. Calculated by finding the velocity of the impactor right before impact with the target <br> tke: The kinetic energy of the target's pendulum after the impact measured in Joules<br> ike: The kinetic energy of the impactor's pendulum after the impact measured in Joules  <br> pike: Post-impact kinetic energy calculated by adding the kinetic energy of the target's pendulum after impact and the kinetic energy of the impactor's pendulum after impact (tke + ike). Measured in Joules.   <strong>Live trap-jaw ant dataset:</strong> <em>mICP_Brunneus_Dataset.csv </em> This contains the dataset of impacts with live trap-jaw ants as the energy source. Information included is as follows: ant: Specifies which ant is performing the strike     <br> group: Specifies the target type where C = Compliant, S = Stiff, FC = Fixed Compliant, and FS = Fixed Steel  <br> strike: Specifies the order of the observation in the amount of strikes performed by the ant for this target type  <br> seq: Specifies the order of the observation in the total amount of strikes performed by the ant across all target types  <br> duration: The amount of time in seconds during which the mandibles were in contact with the target   <br> ake: The kinetic energy of the ant's pendulum after the impact measured in Joules   <br> tke: The kinetic energy of the target's pendulum after the impact measured in Joules  <br> pike: Post-impact kinetic energy calculated by adding the kinetic energy of the target's pendulum after impact and the kinetic energy of the ant's pendulum after impact (ake + tke). Measured in Joules.   <br> ratio: The ratio of ake to tke. Note that for impacts against fixed targets, the target remains stationary after the impact and therefore the tke is NA  <br> dist: The distance (in millimeters) between the ant and the target before the strike   <strong>Annotated Rcode: </strong><em>mICP_DataAnalysis_R_Code.Rmd</em> This Rcode was used to analyze the verification impactor dataset and the live trap-jaw ant dataset. <strong>CAD files:</strong> <em>mICP_CAD.zip </em> The folder contains the necessary CAD files (in .stl format) to 3D print the pendulum housings for the mICP as well as the axel insert described in the publication.