The acrobat ants (Crematogaster scutellaris) build their nest into alive or dead woods of several tree species. When the acrobat ants feel in trouble or if knocking on their trunk, they will immediately exit raising the abdomen. A pheromon for alarm is delivered from the tip of the abdomen. The pheromon breaks out a general alarm in the acrobat ant nest. Any foreigner will be surrounded by an army of aggresive ants that bite it.
In 1st picture, workers of the acrobat ant feed upon the sugary secretion of aphids that sucks the petiole of a holm-oak acorn.
The ants are large group of hymenoptera families with outstanding ecological functions as organisers of the soil ans disseminators of seeds.