Secret to a flea beetle’s powerful jumping skills

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Pesky flea beetles have catapult-loaded back legs, a new study has found.
Credit: JERZY GUBERNATOR / Getty Images

The flea beetle, a type of springy garden pest, uses energy stored in its back legs to catapult hundreds of times their body height in just one millisecond, new research shows.

Insects are jumpy creatures. Their agility when springing themselves off the ground is often a defensive action – either a response to a disturbance or to escape a predator – which means great control is needed over the action.

Despite its impressive height, jumps are a relatively low-energy movement for many insects. In the case of the flea beetle, this is due to an enlarged femur in the insect’s hind legs, acting alongside energy-conserving spring-loaded systems, aided by a rubbery protein material known as resilin.

New research by Konstantin Nadein and Oliver Betz from the University of Tübingen in Germany aimed to unpick the mechanism behind the speedy jumps of flea beetles, which reach mid-leap speeds of up to 3.6 metres per second.

The pair observed seven different species of flea beetle, collected from the edge of a forest near Rottenburg, in Germany.

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A typical insect leg. The flea beetle’s tibia is responsible for its impressive jumping skills.
Credit: Public Domain

They captured frame-by-frame recordings of flea beetles jumping, then dissected and analysed of the beetle’s hind legs.

The findings, in the Journal of Experimental Biology, describe the three phases of a flea beetle’s jump.

In preparation, the beetle readies itself by facing the direction of the jump, flattening its body to a horizontal position, and flexing its hind tibiae.

At take off, the hind tibiae start to extend, lifting the body into the air. In the best jumps, the legs move in unison to launch the body upwards, moving into flight. This extension takes between one and three milliseconds.

The final phase – after take-off – the body moves almost straight up in the direction of the jump, using the energy stored in resilin – an elasticated material made of protein chains found in the insect’s legs.

Indeed, the swollen femur and its attached muscular system are essential to the jump motion, as is an intricate series of extending tendons and ligaments that allow a strong, smooth and rapid motion.

This process allows an extraordinary level of control over direction and velocity during the jump, which Nadein and Betz say is crucial to the beetle’s needs.

“The beetles may use a jump for bridging short distances (on a plant) for which the precise control over the distance, trajectory and speed is relevant,” they write.

“Alternatively, jumps can be used as escape reactions when high-speed reactions are needed.”

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