The hairy worm of the evergreen oak is in fact the caterpillar of the gipsy moth (Lymantria dispar). These caterpillars live all together in nests made of holm oak leaves which are sticked by fine, silky filaments. The caterpillars eat mainly holm oak and cork oak leaves, but also can feed on leaves of fruity trees, oaks or other trees and bushes of the forest. They can be a defoliating plague.
The swatches of long hairs exit from a range of bumps showing two colors, blue in front and red in the rest of the body and at the back. The pictures display two phases of the caterpillar development; the one on the 5th picture has grown more.
[photos Xavier Adot (1st and 5th), Jordi Badia (2nd) and Montserrat Porta (3rd and 4th)]