Insects have some tricks to prevent getting too hot or too cold, but, like a sweater in a blizzard, they only work up to a point. These tricks contribute to what scientists call the thermal tolerance of an insect species.
Look closely at any urban or forest tree and you will find hundreds of insect and mite species scattered here and there feeding on leaves or sap. Most never become pests. A few species become pests only after some change in the environment – like warming temperatures. These are called sleeper species.
Outside of cities, in natural environments, it has long been noted that herbivore abundance and feeding increases near the equator where the climate is warmer. But does this latitudinal-herbivory pattern observed in natural areas apply to cities?
Like we observed in Raleigh, we found that impervious surface was a robust predictor of tree condition, and that one set of thresholds could be used for red maples across the Southeast.