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Phasmatidae (stick insects, walking sticks; subclass Pterygota, order Phasmatodea) Family of large to very large insects, whose common name refers to their resemblance to twigs: this resemblance is often striking and is enhanced by their habit of swaying slowly from side to side. When disturbed, stick insects may become cataleptic and fall to the ground, or else rustle and expand brightly coloured hind wings. They may also produce repugnant odours and secretions. Almost all of the 2000 or so species are found in warmer regions of the world, although two species from New Zealand have established themselves in the Isles of Scilly (Great Britain).