The grass eggar is a common moth which can be seen from October to November, especially where low-growing grasses and plants of the pea family grow. In Maltese it is known as baħrija tas-silla.

The grass eggar belongs to a family of moths known as Lasiocampoidea in which one also finds the oak eggar, known in Maltese as baħrija tal-ballut, and the rare lackey moth which is locally known as malakosoma.

The females are generally noticeably larger than the males, a characteristic of all three species found in the Maltese islands.

The grass eggar is found throughout Europe, North Africa and the Near East as far as southern Russia, but is missing from high altitudes. In some parts of its range, particularly in central Europe, it has become endangered because of eutrophication, agricultural intensification, abandonment of grazing areas and fragmentation of habitat.

In colder countries the moths are seen in the warmer months, especially in August and September.

The female lays its eggs on the ground before winter. The eggs hatch when the days start getting warmer and the caterpillars form a cocoon before summer to hatch in autumn.

Like that of the oak eggar, the caterpillar is covered in protective hairs. It feeds on a variety of grasses and plants of the pea family. When the caterpillar is older, it tends to change its diet to eat more plants of the pea family.

The closely-related oak eggar has a similar life cycle but the adults can be seen flying in August and September. It is common only in the Buskett area.

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