It is a lepidopteran insect of the Thaumetopoeidae family. In their adult instar, the moths show sexual dimorphism, with the females being larger (36-49 mm) (Fig. a) than the males (31-39 mm). They also present other morphological differences. The caterpillars (Fig. b) go through five larval instars, with a size of about 2 mm and a greenish colour with the black head in its first stage, until they reach 40 mm and turn grey-brown in the fifth instar. Their bodies are covered with whitish hairs and on the dorsal part, they have reddish spots with orange urticating hairs that appear in the third instar.
The first moths appear in the second week of June, in cold places, and in the second week of July, in warmer places, up until September. In three days, they lay their eggs on the leaves. The caterpillars will come out after five weeks. They are gregarious; at first, the nests are very simple and when the cold arrives they build the typical sack-shaped nest (Fig. c) with silky white hairs on the sunniest part of the tree; they are active at night and leave the nest to feed. During January, February and March (depending on the climatic conditions of the area) they descend from the pines, forming characteristic processions, looking for a good place to bury themselves and become chrysalides. Not all moths are born in the first year; an significant part is born in the next 2-3 years.
In urban areas or areas frequented by man or animals, they can be very dangerous due to the urticating hairs of caterpillars, especially by injuries to the eyes and respiratory tract. We must also consider the aesthetic damage caused by the sack-shaped nests, defoliation, as well as the social alarm they generate.
To avoid any problems, the caterpillars must be prevented from reaching at least the third instar, since that is when they start growing urticating hairs. A single treatment with plant endotherapy (ENDOterapia Vegetal®) between September and November (depending on the geographical area and climate) controls the pest entirely, with 100% efficiency. This way, caterpillars are eliminated just when they start to devour the leaves and they are prevented from reaching their urticating stage. Therefore, there are no risks of rashes and other anaphylactic reactions in people and animals.