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.
The adult is a fat and hairy moth outstanding for sexual dimorphism.
The males -images 6th and 7th- are brown with a golden hue with forewings crossed by a series of darker lines roughly in zigzag or continuous letter “m” and lighter, orangish and more uniform shade eventually with dark, straight, slightly blurred narrow lines as rays over the veins. Males stand out for their pair of large feathery or pectinate antennae as they were a long-eared bat.
On the other hand, the females are white coloured with the same dark brown lines on the front of the forewings, with brown legs and filiform antennae, not feathery or pectinate. The name gipsy moth refers to the females.
Both sexes have blue eyes, although pale in females and almost black in males. One fringe as a chessboard beautifies the edge of the wings.
The caterpillars are seen in spring and the adults in July, while the rest of the year is spent in the egg phase. The females agglutinate the eggs in a viscous golden mucilage that they segregate and stick on the bark of trees, preferably in cork oaks and holm oaks. Fortunately, being a species capable of causing pests, the gipsy moth achieves only one generation per year.
The male specimen in image 7th has a particular colour aberration, a wide light stripe, on its right forewing.
[photos Xavier Adot (1st and 5th), Jordi Badia (2nd, 6th and 7th) and Montserrat Porta (3rd and 4th)]