Roaches & their escape trick

Cockroaches are not just insidious home invaders, a new study finds; they are also brilliant escape artists. A roach can flip under a ledge by swinging its body around like a pendulum and hanging on underneath. It uses hooklike claws to hold on firmly.

The movement occurs in milliseconds, too fast for the human eye to process. To the naked eye, it appears as if the cockroach has disappeared. “It was a serendipitous discovery,” said Robert J Full, an integrative biologist at the University of California, Berkeley, and an author of the study, appearing in the journal PLoS One.

Brian McRae, a Berkeley undergraduate who is also listed as an author, was working on the project and noticed that the cockroaches disappeared at the end of a ledge.

A closer look at video recordings revealed that they ran full speed towards the end and then dived off, grabbing the edge with their claws (at times using a single leg).This may be why “sometimes when we’re chasing them they are just gone,” Full said.The group also looked at geckos and found that they exhibited the same behaviour.

The researchers have now joined forces with Ron Fearing, a computer scientist at Berkeley, to try to develop a robot with the agility of a cockroach.

What strengthens the mantis shrimp...

The Indo-Pacific creature known as the peacock mantis shrimp is not a true shrimp but its own species of crustacean. It has bright red appendages that can smash through mollusk shells, the heads of small fish and even glass aquarium walls.

Researchers now report what makes these appendages, called dactyl clubs, so powerful. “We discovered that they have a unique composite structure – there are three different regions inside the club,” said David Kisailus, a chemical engineer at the University of California, Riverside, and an author of the study, published in Science.

The face of the club is composed of a highly crystallised form of calcium phosphate, the mineral found in bones. This gives it a high compressive strength. Under that are rods of material called chitin, which helps prevent fractures from growing.

The final region, along the sides of the claw, is also made up of chitin and helps place the rest of the club under compression. Any damage “is so localised that the clubs are still functional,” Kisailus said.

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