They're the tiny, fuzzy yellow or brown balls on oak leaves and branches. You could spot one or two, then dozens around the same tree. Oak galls are the result of gall wasps. Inside the galls are ...

A citizen science project was conducted in 2007 to survey the oak gall wasps of Finland. More information on the oak gall wasp survey's site (in Finnish and Swedish) In 2016, we conducted a citizen ...