Earliest plant defences against herbivores
Conifers are also able to repel insect damage with a gummy substance called resin. Insects are often caught in the resin which has proved to be a good fossilizing medium called amber. The first amber containing flying insects appeared 100 million years ago and includes representatives of all major insect groups known today. Each group has developed its own characteristic way of flying. Dragonflies have two pairs of wings which flap up and down synchronously, bees and wasps have linked the fore and hind wings together with hooks, butterflies have overlapped the wings, hawkmoths have reduced the hind wings considerably in size and latched them onto long narrow fore-wings with a curved bristle, beetles have the front pair modified into thick covers which protect the rear flying wings, and flies use only the front pair of wings for flight with the hind wings reduced to tiny knobs.
Although insects were the first animals to invade the air, they nevertheless fell prey to their arachnid adversaries, the spiders, who evolved the ability to spin webs between branches and thereby trap and consume flying insects.