Thaumetopoea pityocampa Schiff.

Lepidoptera. - fam. Bombycideae

Synonyms : Cnethocampa pityocampa - Gastropacha pityocampa. French name : Bombyx processionnaire du Pin.
Size : 30 to 40 mm.
Visible Damage: Gnawed or partially eaten pine needles.
General Character and Habits: In southern France this butterfly often invades entire districts planted in pines and its caterpillar stage causes extensive damage.
      The butterfly appears in June or July and the female lays her eggs around the pine needles, forming a ring which appears like a small hand muff.
The white spot in the crown is a caterpillar nest on a Pinus pinaster
      After one month, the caterpillar hatches from the egg and immediately it begins to eat the nearest needles and to weave a silk nest where it eats all of the needles incorporated therein. When this supply of needles is consumed, the caterpillar repeats the process, each time building a larger nest with more needles to be consumed. The caterpillar continues to build progressively larger nests, each time consuming more needles until it reaches about 20 mm. length. Then the caterpillar builds a large white silky pocket at the end of the pine shoot. This pouch has an ovoid or conical shape, incorporating many needles in its silky threads. During the daytime the caterpillars take refuge in their pouches and then at night they go out, moving in procession, to feed on pine needles. They molt (shed their coats) as they grow larger through the winter, reaching about 40 mm. in length by the next June. Then they drop from the pine tree and bury themselves in the soil where they have their chrysallis stage in a cocoon.
      The caterpillars have irritating hairs on their bodies which detach and embed into human skin with direct contact. This causes a severely painful itching sensation, so it best to avoid touching the catepillars and to be especially cautious with dry windy conditions.
Method of Control: Cut the shoots with the silky nests, best on a rainy morning or cold winter day, and burn them immediately.

Observations in the Arboretum: These caterpillars were observed so far on the following Pinus species:
Pinus nigra (the most common pines in the region above 300 meters)
Pinus sylvestris
Pinus ponderosa
Pinus pinaster
Pinus coulteri
Pinus attenuata (curiously on this species the caterpillars seem to have a problem to establish a nest, migrating often to another shoot, as if the tree was able to defend itself)

Pinus ponderosa infested by young caterpillars. Size: 319 Ko
Very young nest on a Pinus ponderosa. The empty eggs can be seen behind the buds (dark colour), while some very small caterpillars are feeding on the needles (right side). The nest encircles the shoot. (Click on the photo to enlarge it to see all details.)
Photo taken on the 20 August 2001.

Pinus ponderosa infested by young caterpillars.
The caterpillars just left their previous nest to go feeding on another shoot of the same branch and build a second nest.
Photos taken on the 6 September 2009 on a Pinus ponderosa.