Kick With A Punch

Grasshopper

Grasshopper
(click to enlarge)

If you catch a grasshopper in your hand, you can feel it kicking as it tries to get free. The kick is surprisingly powerful. This is due to a catch mechanism in the joint between the femur and the tibia. The femur is swollen to accommodate large and powerful extensor muscles. The muscles contract slowly relative to the movement of the leg. The muscles bend the joint and transfer force to the joint the way a catapult might be loaded with force. When the muscles are fully contracted, the catch releases and the tibia hits the enemy with force and speed. The spines on the tibia concentrate the blow.

The large force generated by the tibia could damage the joint if the blow missed the enemy. The grasshopper leg is adapted for that contingency. The tibia has a groove in the cuticle near the joint that will buckle if excess force is applied. The buckling of the cuticle dampens much of the force that might otherwise damage the joint. The hind leg is only one of many defenses that grasshoppers have against predators and parasitoids.

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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