section_path: Phylogeny and evolution/Evolutionary history
section_name: Evolutionary history
paragraph_text: Evolutionary history
  
  The oldest fossil that may be a primitive wingless insect is Leverhulmia from the Early Devonian Windyfield chert. The oldest known flying insects are from the mid- Carboniferous, around 328–324 million years ago. The group subsequently underwent a rapid explosive diversification. Claims that they originated substantially earlier, during the Silurian or Devonian (some 400 million years ago) based on molecular clock estimates, are unlikely to be correct, given the fossil record.
  
  Four large-scale radiations of insects have occurred: beetles (from about 300 million years ago), flies (from about 250 million years ago), moths and wasps (both from about 150 million years ago).
  
  The remarkably successful Hymenoptera (wasps, bees, and ants) appeared some 200 million years ago in the Triassic period, but achieved their wide diversity more recently in the Cenozoic era, which began 66 million years ago. Some highly successful insect groups evolved in conjunction with flowering plants, a powerful illustration of coevolution. Insects were among the earliest terrestrial herbivores and acted as major selection agents on plants. Plants evolved chemical defenses against this herbivory and the insects, in turn, evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using warning colors.