Phasmid species that inhabit colder environments are less likely to have the ability to fly

A vast majority of insects can fly, but some cannot. Flight generally increases how far an individual can travel to access mates, enables the exploitation of additional food resources, and aids in predator avoidance. Despite its functional significance, much remains unknown about the factors that influence the evolution of flight. Here, I use phylogenetic comparative methods to investigate whether average annual temperature or wind speed, two components of the flying environment, is correlated with the evolution of flight using data from 107 species of stick and leaf insects (Insecta: Phasmatodea). I find no association between wind speed and flying ability in this clade. However, I find that colder temperatures are associated with the lack of flying ability. This pattern may be explained by the additional metabolic costs required for insects to fly when it is cold. This finding contradicts previous patterns observed in other insect groups and supports the hypothesis that cold temperatures can influence the evolution of flight.