Nearly half of all insect species worldwide are in rapid decline and a third could disappear altogether, according to a study warning of dire consequences for crop pollination and natural food chains."Unless we change our way of producing food, insects as a whole will go down the path of extinction in a few decades," concluded the peer-reviewed study, which is set for publication in April.The recent decline in bugs that fly, crawl, burrow and skitter across still water is part of a gathering "mass extinction," only the sixth in the last half-billion years."We are witnessing the largest extinction event on Earth since the late Permian and Cretaceous periods," the authors noted.The Permian end-game 252 million years ago snuffed out more than 90 percent ).