<P> The most recent understanding of the evolution of insects is based on studies of the following branches of science: molecular biology, insect morphology, paleontology, insect taxonomy, evolution, embryology, bioinformatics and scientific computing . It is estimated that the class of insects originated on Earth about 480 million years ago, in the Ordovician, at about the same time terrestrial plants appeared . Insects evolved from a group of crustaceans . The first insects were land bound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so . The oldest definitive insect fossil, Rhyniognatha hirsti, is estimated to be 407 to 396 million years old . Global climate conditions changed several times during the history of Earth, and along with it the diversity of insects . The Pterygotes (winged insects) underwent a major radiation in the Carboniferous (356 to 299 million years ago) while the Endopterygota (insects that go through different life stages with metamorphosis) underwent another major radiation in the Permian (299 to 252 million years ago). </P> <P> Most extant orders of insects developed during the Permian period . Many of the early groups became extinct during the mass extinction at the Permo - Triassic boundary, the largest extinction event in the history of the Earth, around 252 million years ago . The survivors of this event evolved in the Triassic (252 to 201 million years ago) to what are essentially the modern insect orders that persist to this day . Most modern insect families appeared in the Jurassic (201 to 145 million years ago). </P>

When did the first insects appear on earth