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Jutta Arctic

Oeneis jutta

  • Name also: Baltic Grayling
  • Family: Brushfooted Butterflies – Nymphalidae
  • Subfamily: Browns – Satyrinae
  • Wing span: Medium-sized(–large), 45–60 mm, (1.76–2.34 in.). Females larger than males.
  • Wing upper side: Dark brown–light brown. Margin with row of eyespots surrounded by pale yellow or orange rings. Eyespot lacking white centre.
  • Wing underside: Forewing orangey brown or brownish beige, margin and tip grey. One or many black eyespots with white centre. Hind wing grey with greyish brown lateral band. Back corner of hind wing with black eyespot with white centre surrounded by orange ring.
  • Habitat: Wooded bogs.
  • Flying time: Southern Finland earlyJune–mid-July. Northern Finland late June–early July.
  • Overwintering form: Caterpillar (overwinters two seasons).
  • Larval foodplant: Cottongrasses (Eriophorum) and possibly sedges (Carex).
  • Endangerment: Near threatened.

The jutta Arctic always rests with its wings pressed together, which makes the upper side difficult to study without catching it. The species is reminiscent of the rock grayling as well as the Norse and Arctic graylings, but their habitats do not overlap much. They are all large Browns with grey and brown-chequered undersides on the hind wings and the same colours on the forewings too. Arctic grayling has no eyespots at all, however. The jutta Arctic also has an eyespot on the underside of the apex, which sets it apart from the rock and Norse graylings. Additionally, rock grayling’s hind wings are divided into an orange basal part and a yellowish-white outer part, while the jutta Arctic’s basal part is orangey brown and the outer part is brownish beige with varying amounts of black.

Like a number of other species that can be found in Lapland, jutta Arctic caterpillars need two winters before entering a cocoon to emerge as butterflies.

Double-winterers

Of the butterflies that can be found in Finland, several species – especially in Lapland where the summers are short and cool – overwinter twice, usually as caterpillars (sometimes the first year as an egg), but never as adults. Other species that overwinter twice are:
(1) Arctic grayling, Norse grayling
(2) Arctic ringlet, Arran brown, Arctic woodland ringlet, Lapland ringlet and Dewy ringlet
(3) Alpine grizzled skipper and often also Northern grizzled skipper
(4) Dusky-winged fritillary, Polar fritillary, Mountain fritillary and Bog fritillary
(5) Lapland fritillary

Butterflies that overwinter twice are often abundant every other year and weak in between. The jutta Arctic’s and e.g. Arran brown’s fluctuating numbers are due to the parasites that live on the larvae. Species that overwinter twice have two different stages of larvae alive during the same summer. When the older larvae’s parasites lay eggs, the new parasites attach themselves to the older larvae, and if the number is small to begin with a relatively large proportion of larvae die. The next year the small number of parasites on larvae that are over one year old lay their eggs, and because they and the parasites are small in number a bigger proportion of first-year larvae survive until the next year, go through the cocoon stage, and emerge as butterflies.

Other species from the same genus
Other species from the same group

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