Adult: The female is 45 to 65 mm in span and 25 to 28 mm in body length; whitish wings, with some black spots, of which, a V-shaped, is very characteristic in the anterior wings. Body very robust, hairy, yellowish. Abdomen very bulky and heavy, characteristic that makes them unable to fly and clumsy in the face of walking. Finely toothed antennas The male is quite smaller, having 35 to 40 mm in span and 18 to 20 mm in body length. The wings, of yellow-earthy background color with dark zigzag spots, brown-blackish, abundant, especially in the previous pair. Abdomen much thinner than that of the female, almost conical, covered with yellowish-brown hairs. They are good flyers. Feathery antennas.
Placement: In the form of yellow plastones of 3 to 4 cm in length and 1.5 to 2 in width, formed by the eggs and the hairiness of the abdomen of the female, united by a special binder that secretes it. The number of eggs that each female lays varies between 250 and 500.
Caterpillar: Newborn measures from 3 to 3.5 mm. They are very hairy and their general coloration is blackish. During their development they change coloration, after the dumb ones, but the grayish color always predominates. The grown caterpillar is hairy and presents in the thoracic segments and the first abdominal, dark blue tubers and, in the remaining abdominal segments, red tubers, all with very long hairs. During the growth the caterpillars make four or five changes. The females come from the caterpillars that have made five changes, that is, from six stages, and the males, from which they made four, that is, from five stages. The size of the caterpillars grown ranges from 45 to 70 mm in length.
Chrysalis: dark brown, without silky cocoon; it is provided at the apical end with silky hairs, by means of which it remains subject. It is possible to differentiate perfectly the chrysalids that are going to give rise to female imagos because they are much larger and have an almost cylindrical abdomen, while in those of the males it is almost conical.
Depending on the intensity of the pest, the defoliation may be incomplete or total; if it is total and lasts several years, the death of the affected trees may occur.
Apart from the damage to growth prevents fructification, very important in some of the affected species.
Among the egg parasites are the Hymenoptera Anastasus disparus and Oencyrtus kuwanae.
Parasites of the caterpillars of the first important stages are the braconids Apanteles vitripennis, Apanteles melanoscelus and Apanteles liparidis; In more advanced stages, the Tricholyga segregata and Exorista larvarum dipteran snakes stand out.
Among the parasites of pupae, the calcid Brachymeria intermedia stands out above all.
The carábido Calosoma inquisitor is a leading caterpillar predator of Lymantria dispar.
In incipient pests traps with female pheromones can be used to attract males.