This document discusses how phytophagous insects feed and evolve to use new host plants. It proposes that insects initially specialize on a single host, but some individuals may erroneously feed on novel plants, expanding their diet. This can lead to oligophagy and the beginning of reproductive isolation between populations as their attacked trait spaces separate. Over time, isolation may strengthen as trait spaces diverge but also relax as they converge again, like the movement of pincers - this is known as the "gape-and-pinch model". Host shifts and evolution of new specialist species occurs in stages as insects diversify their use of available plant traits.