Far more informative, overall - https://en.wikipedia.org/wiki/Oak_processionary - including:

>The moths are widely distributed in central and southern Europe, and are occasionally found as far north as Sweden. In the southern countries of Europe the populations are controlled by natural predators, but these predators are not present in northern Europe.

It'd be very convenient if the caterpillars had some exclusive predator which could be released in areas suffering aggressive outbreaks...