The Mantis Grip Evolved at Least Seven Times. It Kept Coming Out Different.

A praying mantis, a water scorpion and a giant water bug all catch dinner the same way, by snapping a folding foreleg shut on it like a jackknife. Look closely, and the knives follow different specifications.

Insects have invented these grasping front legs, known as raptorial legs, on no fewer than seven separate occasions. The trap works identically each time: prey gets clamped in the hinge where the femur meets the tibia, the leg's third and fourth sections. At a glance, the versions look interchangeable.

Matching jobs might be expected to yield matching tools, a pattern called convergent evolution. A team from Kobe University, the Ishikawa Insect Museum and the Hyogo Prefectural Institute of Technology checked. They measured every foreleg segment in six of the groups, using the ordinary front legs of close relatives as a stand-in for the ancestral starting point. Students skilled at insect hunting collected specimens in Japan.

The results, published July 7 in Scientific Reports, show each group's grasping leg has its own distinct proportions. The lineages drifted in loosely similar directions, but none converged. Water scorpions and giant water bugs, the aquatic hunters, varied even among themselves. The other four legs showed no shared trend.

The one consistent change sat elsewhere. In every group, a raptorial foreleg came packaged with a wider head and a stretched, slimmer prothorax, the body segment behind the head.

The researchers suggest that when one function can be served by many shapes, evolution gains room to diversify. Why each lineage settled on its design remains open.

Insects have sat the same exam at least seven times. Of the six papers graded, all pass and no two show the same working.

Read the full story at Science Japan, September 24, 2026

Hot Take: Any field guide still lumping these hunters together as mantis-like owes six lineages a formal correction, preferably in millimeters.