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Dryad

Ballistic high powered spider webs overcome dangerous prey defenses

Cite this dataset

Narendra, Ajay et al. (2024). Ballistic high powered spider webs overcome dangerous prey defenses [Dataset]. Dryad. https://doi.org/10.5061/dryad.2fqz612xt

Abstract

Spiders exhibit a remarkable range of silk-based predatory tactics, but usually avoid capturing ants since they are highly defended. Here we report on a spider that exclusively hunts aggressive Oecophylla ants by isolating and immobilising individual workers using a extraordinary ballistic snare that lures ants, then propels them into its core web at extreme speed. By serial arrangements of tension lines, small pre-strains of the silk are sufficient to reach power densities of up to two megawatts per kilogram actuator mass, which surpasses the performance of other natural spring-actuated systems. Thus, the ultimate prey specialisation in these spiders has led to the evolution of extreme web performance.

README: Ballistic high powered spider webs overcome dangerous prey defenses

[Access this dataset on Dryad] https://doi.org/10.5061/dryad.2fqz612xt

Description of the data and file structure

We have provided four Matlab files. This file can be accessed through any of the recent version of Matlab.

a. propostira_data.mat: contains raw data and outputs (details below)

b. propositra_analyses.m: is the Matlab script to load and run propostira_data.mat

c. acceleration.m: is a function that should be saved and downloaded in the same folder with other files. No need to open this, but required to run propositra_analyses.m

d. smooth.m: is a function that should be saved and downloaded in the same folder with other files. No need to open this, but required to run propositra_analyses.m

Contents of propostira_data.mat:

This is a matlab structure with data for six attack sequences. The structure is organised as follows:

name: filename contains the video number (ranges from 1 to 6), date (Year,month,date), frames per second (fps), outcome (no prey=failed capture or capture=success). Note: the first file (row 1), the ant bit the snare, but did not get hauled up. All the remaining five clips are of successful captures.

ant_pos: x,y coordinates of head position (pixels)

scale: scale information (pixels)

mass: weight of the ant (mg)

mass_kg: weight of the ant (kg)

acceleration: shows acceleration for each frame (m/s^2)

acceleration_max: contains the maximum acceleration (m/s^2)

velocity: shows velocity for each frame (m/s)

velocity_peak: contains the maximum value of velocity (m/s)

How to run the script

Open propostira_analyses.m in Matlab

Line 10: change the n=* to select different individuals (rows).

Line 12: change scaleCm: to match the scale value for each video. The scale for each video is mentioned in the same line

Line 13: change fps: to match the scale value for each video. The fps for each video is mentioned in the filename

Line 15: change ySize: to match the ySize value for each video. The ySize for each video is mentioned in the same line

To run the script and calculate variables without saving any outputs, comment (add %) to Line 70

The result:

In addition to displaying the above variables, the script will generate two plots. First plot shows acceleration (primary Y axis) and velocity (secondary Y axis) against frame number. Second plot shows the trajectory of the snare (video 1) and of the ant (videos 2-6).

Supplementary videos

We have provided three Supplementary videos.

Movie S1: filename: 'propostira_video_S1.mp4': Construction of the conical snare. 

Movie S2: filename: 'propostira_video_S2.mp4': Ballista spider wraps the cone with thinner silk, constructs a tension bundle line and fan-shaped array of tension lines.

Movie S3: filename: 'propostira_video_S3.mp4': Worker of Oecophylla smaragdina is attracted to the conical snare, bites it, and gets propelled to the core web of the Ballista spider.

Methods

Highspeed video data was collected in the field at Cape York. 

Videos were processed and analysed in the lab. Collected silk was analysed in the lab using different microscopy techniques.

Funding

Australian Research Council

European Research Council