Kingdom: Animalia
Subkingdom: Eumetazoa
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Lepidoptera
Superfamily: Lasiocampoidea
Family: Lasiocampidae
Subfamily: Lasiocampinae
Genus: Lasiocampa

This is one of the two species of the genus Lasiocampa in Croatia and they can be easily distinguished even by the color of their wings. The wings of the male Oag eggar are dark brown while in Grass eggar they are light brown. Females are yellow in Oak eggae and more brown in Grass eggar. In this species, both males and females fly mostly at night, but sometimes males can be seen flying during the day. Adult moths are active from July to September in one generation. This species inhabits overgrown grassland habitats, rocky areas, pastures and forest edges. Caterpillars of this species feed primarily on grass but older caterpillars also feed on other herbaceous plants such as legumes. This species inhabits most of Croatia but is mostly lacking in mountainous areas.