Oak tree with its gall

3D Model

A phenomenon that arouses amazement and fascination due to the originality of the biological mechanisms involved, is that which concerns the formation of ‘galls’, i.e. those singular ‘outgrowths’ (technically called ‘caecids’), with strange and unusual shapes, that can often be seen on the leaves and branches of numerous plant species. These structures are the plant’s response to an external aggression: the most frequent and significant are those that form as a reaction to a stimulation mediated by certain insects (stinging and egg laying) or other organisms (mites, fungi, bacteria and viruses). With regard to oaks (Quercus sp.), there are various gall insects belonging to the same genus, including Andricus quercustozae, whose gall produced by the plant is spherical, light and corky.