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Walkingsticks

phasmids insects species eggs

Walkingsticks are insects with a long, thin body, lengthy delicate legs and a brown-green color which gives them a striking resemblance to a twig. Walkingsticks are in the family Phasmidae in the order Orthoptera, which also includes the grasshoppers and crickets. There are almost 2,500 species of walkingsticks (phasmids), ranging in size from 1 in (2.5 cm) to 1 ft (30 cm), the largest species occurring in the tropics. Some phasmids resemble leaves (rather than twigs) and are called leaf insects.

A walkingstick. Photograph. © Art Wolfe/The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.

All species of phasmids are herbivorous and are found on or near vegetation. Often, a phasmid will look like the plant on which it is feeding, an adaptation known as protective resemblance, which blends these insects with their surroundings and protects them from predation. Walkingsticks not only resemble twigs, they also walk with an odd, rocking motion which makes them appear to be a stick being blown in the wind. If phasmids are attacked by a predator then delicate legs break off so the insect can escape. Some species of phasmids when attacked spray a foul-smelling fluid from glands on their thorax. In large numbers, phasmids can cause extensive defoliation damage to trees, but these insects are otherwise harmless.

After copulation, female phasmids simply lay their eggs while feeding, scattering them on the ground. Some species project their eggs with a flick of the abdomen while others place their eggs in a protected crack or crevice. The eggs usually hatch within two years. Thus, the majority of walkingsticks are usually found every second year. Young phasmids (nymphs) resemble adult insects, and grow in a series of stages (instors) to the adult stage, a type of development known as incomplete metamorphosis.

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