Southern wood ant - nest, Heeswijk-Dinther, Netherlands

Nest impression of this forest ant. In this case, it is situated on the inside of an old tree bark, but in general it looks as a massive bump or pile of organic material: leaves, twigs, the like. A single nest can contains hundreds of thousands of female workers, here in the bottom of the photo you see plenty. Sometimes nests split yet are still part of the same even larger colony.

This species is highly aggressive, they come out angrily by the thousands when provoked or when foraging. Few species can withstand this relentless mob of jaws and acid spraying abdomens. All but woodpeckers skip this meal.