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First published online August 30, 2006
Journal of Experimental Biology 209, 3510-3515 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02401
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Efficiency of antlion trap construction

Arnold Fertin* and Jérôme Casas

Université de Tours, IRBI UMR CNRS 6035, Parc Grandmont, 37200 Tours, France


Figure 1
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  		Fig. 1. Hypothetical relationship between predation cost and trap angle. The shaded part of the graph corresponds to angles greater than crater angle ({alpha}c), which cannot be achieved because of the physical properties of sand. {alpha}WO is the theoretical angle without off-centring.

 

Figure 2
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  		Fig. 2. Reconstruction and 3D measurements of an antlion trap. (A) Diagram of the set-up. The light source projects a shadow of the edge of the plane on the scene. The edge of the plane and the shadow are projected onto the normalised image plane of the camera, and the resulting image is used to reconstruct the three-dimensional scene in the camera's reference frame O(X,Y,Z). (B) Reconstruction of the trap surface. (C) Geometric variables measured on the surface of the trap (green line) and on the conical surface (black line). The figured off-centred position is exaggerated for the purpose of illustration.

 

Figure 3
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  		Fig. 3. Changes in {Delta}angle (A) and {Delta}RMSE (B) as a function of off-centring. The straight line corresponds to the linear model fitted on the data. The open circles are data points and the closed circles are the predicted values of {Delta}angle and {Delta}RMSE in the absence of off-centring, making it possible to obtain RMSEwo and {alpha}wo: RMSEwo= {Delta}RMSE(0)+RMSEc and {alpha}wo={alpha}c-{Delta}angle(0).

 

Figure 4
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  		Fig. 4. Distribution of the angles achieved in antlion constructions. The number of classes is given by Yule's formula (k=5.53). The bars with solid lines correspond to {alpha}wo and {alpha}c, and the dotted lines indicate the 95% confidence intervals for these angles.

 

Figure 5
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  		Fig. 5. Linear changes over time in capture as a function of off-centring.

 




© The Company of Biologists Ltd 2006