What type of creature is a gatekeeper?

The gatekeeper ("Pyronia tithonus") is a species of butterfly found across Europe.

It is a member of the subfamily "Satyrinae" in the family "Nymphalidae". A similar species is the meadow brown; the two species can be difficult to distinguish with closed wings, since the underwing markings are very similar. However, the gatekeeper tends to rest with its wings open, whereas the meadow brown usually rests with its wings closed. The gatekeeper is also smaller and more orange than the meadow brown and has double pupils on its eyespots.

The gatekeeper is a characteristic field-margin species; it feeds on grasses as larvae and nectar as adults. The larvae of the "Satyrinae" all feed on grasses, such as rough meadowgrass ("Poa trivialis"), smooth meadow grass ("Poa pratensis"), and sheep's fescue ("Festuca ovina"); they are usually green or brown. The pupae are a flimsy chrysalis either hanging upside down or lying in grass. The adults are often found around blackberry plants. The adult butterfly has a short proboscis and the shallow flowers of the blackberry provide an excellent nectar source.