Image: Bettina Bläsing / JEB
Reading Spooky locusts can obviously neither see nor perceive abysses with their feelers: If a gap breaks in their path, the insects will not stop until their front legs lose ground under their feet. Only then they examine the gap in front of them with the feelers and cross them, discovered biologists from the University of Bielefeld in studies on the locust species. Bettina Bläsing and Holk Cruse describe their investigations in the journal Journal of Experimental Biology (vol. 207, p. 1273). As ghost scares (Aretaon asperrimus) move forward, they are constantly probing the terrain with their long antennae. In doing so they hit an obstacle, stop the insects and examine it exactly, before they climb over it. The animals behave quite differently, however, when there is an abyss in front of them, Bläsing and Cruse discovered: The insects just keep on walking? although their antennae have long since lost contact with the ground. Only when the first forefoot enters the void, the grasshoppers notice the gap before them and stop. Obviously, the sense of sight plays no role in the discovery of the gap, because the insects behaved the same when their eyes were covered.

To further investigate the tactics with which the ghostly horrors overcome abysses, the researchers confronted some animals with gaps of different widths and recorded the movements on video. The biggest gap at 5 centimeters was about as long as the insects themselves. Overcoming a gap always followed the same pattern: First, the insects fumbled around with their feelers until they had contact with the other side. This took up to fifteen minutes, depending on the width of the abyss. When the opposite side was successfully felt, the animals stretched until they could place their forelegs firmly on the other side.

Only when the front legs had a firm footing did the insects gently invert their mid-legs. After another test, whether all legs are on firm ground, they finally released the hind legs and overcame the gap. Bettina Bläsing now wants to use the knowledge about this crossing technique to develop a computer-simulated grasshopper that behaves just like a real grasshopper. All previous attempts had failed because the cyber insects had simply continued on abysses.

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