Oberthür's grizzled skipper

Species of skipper butterfly genus Pyrgus

Oberthür's grizzled skipper (Pyrgus armoricanus) is a species of skipper (family Hesperiidae).

Pyrgus armoricanus has a wingspan of 24–28 mm. Both wings have a white fringe along the edges. The upperside of the forewings is dark brown with well developed white markings. On the recto of the hindwings there are clearly visible grayish marks. The underside of the hindwings shows a pale reddish brown colour with a large pale discal spot and light coloured veins. The males and females are similar in appearance. Like all Pyrgus species, Pyrgus armoricanus can be very difficult to identify in the field. The upperside of the forewings are often noticeably darker brown than other Pyrgus species, especially when fresh, with clear white markings. It resembles some smaller races of large grizzled skipper (P. alveus). It is slightly larger than Pyrgus malvae. This species is also quite similar to Pyrgus carthami and Pyrgus serratulae. Without a genital examination, there is a high risk of confusion, especially with butterflies of the Pyrgus alveus complex and with Pyrgus cirsii. Compared to Pyrgus alveus, however, the white spots on the upper side of the hind wing are clearly lighter. The eggs are yellowish, roundish and flattened, with numerous, strong longitudinal ribs. The caterpillars have strong short hairs. They are mostly dark brown to gray brown, rarely greenish brown or reddish brown with a black head. Pupae are strongly bluish frosted with black dots and dashes on the back.

Pyrgus armoricanus is distributed from northwest Africa across southern and parts of central Europe to southern Scandinavia. To the east, the distribution area extends to southern Russia and across Asia Minor to Iran.

The habitats of Pyrgus armoricanus include a wide range of open land locations with raw soils. In addition to semi dry and sandy grasslands, this can also be, for example, ruderalized areas and footsteps on unpaved paths. Depending on the natural area and soil substrate, there can be very different habitats. The larval habitats always have sparse and short grass vegetation. In addition to poor grasslands, mesophilic grassland stands can also be populated, provided they have a sufficient number of open ground areas (including molehills, roadsides, median strips of unpaved roads). The females lay their eggs individually on the underside of the leaves of host plants. Eggs are laid on plants in full sun, which mostly grow over open soil or dark litter (e. g. also dry floating debris on river banks). Soil with little vegetation and dark subsoil ensure rapid warming. The majority of the habitats are level locations, south sloping slopes are used comparatively less often. Extremely xerothermic locations are hardly populated, even with abundant host plants. The caterpillar sites indicate a certain moisture requirement of Pyrgus armoricanus for larval development. Small and more isolated habitats are only populated with a strong increase in or after very favorable years. In these, Pyrgus armoricanus shows particularly strong population fluctuations with temporary complete extinction on individual areas, which is to be interpreted as an indication of a metapopulation structure. The imagos regularly look for flowers to take in nectar and use a wide range of flowering plants. In southern Scandinavia (Sweden and Denmark), however, the main larval food plant is Filipendula vulgaris and to some extent also Helianthemum nummularium. Potentilla verna agg. and Potentilla reptans have been documented as larval food and egg laying plants in Bavaria so far. The caterpillar overwinters.