Boloria selene, known in Europe as the small pearl-bordered fritillary, is a species of butterfly of the family Nymphalidae. It is found across Europe, Asia and North America, and feeds exclusively on violets in its larval stages. This species prefers wet grassland habitats, where its larval food source, violets, are found. It overwinters in its larval stage, and eggs hatch in the late summer to early autumn. Members of this species are prey for multiple types of birds and other insects.

Due to modern agriculture, most of the grassland habitats that sustain Boloria selene are fragmented or lost all together in favor of farmland.

Appearance

The small pearl-bordered fritillary is similar to the pearl-bordered fritillary but has black chevrons on the edge of its wings, a large central black dot on each wing, and white pearls on the underside. Males tend to be smaller than females, with a wingspan of 35 to 41 mm. Females are 38 to 44 mm in length. Though the small pearl-bordered fritillary is similar to the pearl-bordered fritillary it is much brighter in color because the pearl-bordered fritillary emerges from its pupa earlier. Seitz - A. selene Schiff. (= euphrosyne Bgstr., euphrasia Lew., silene Haw.) (67g). Forewing above and beneath very similar to tliat of the preceding [selenis]. Hindwing beneath with the median band distinct but not broad, the costal spot of the band, the large tooth above the apex of the cell and the one below the cell-end being vividly silvery like the marginal lunules; the broad interspace between the median band and the marginal lunules is leatheryellow and bears below the apex and above the anal angle two large dark cinnamon clouds; obsolescent silvery selenia bands extend from the costal and abdominal margins towards the centre of the wing.

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File:Boloria selene MHNT CUT 2013 3 21 Sornac Dos.jpg|Dorsal side

File:Boloria selene MHNT CUT 2013 3 21 Sornac Ventre.jpg|Ventral side

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Distribution

The species is widespread across central and northern Europe, North America, and through Asia to Korea. Specifically, it can be found in places like Germany, the United Kingdom, and Sweden and in the Midwestern United States in places like Iowa and the Dakotas. In the United Kingdom, Boloria selene is widespread across upland and western Britain, but is not found in central, eastern England or Ireland. Its range appears to be stable through much of Europe but declines have been reported in at least nine countries, including England.

This species is found across Europe Adult small pearl-bordered fritillaries feed on the following plants:

  • Bramble
  • Thistle
  • Bugle (Ajuga reptans)

Migration habits

This species is well known to migrate short distances during its reproductive stage, but does not appear to make any long-distance migrations that cross over unsuitable habitats such as farmland and urban areas.

Predators

Small birds appear to be major predators of both larval and adult stages, including introduced ground birds such as pheasants that were introduced in the UK for sport hunting (in quantities of almost 40 million birds according to a study done on ground birds' impact on local wildlife). However, no major decline was detected from the introduced predators alone, as there was no significance between reduced adult emergence and increased ground birds. In a study of ambush bugs, Boloria selene was identified as a prey, although predation rates were not studied.

Genetics and local adaptation

A study using North American populations found that sibling mating events of this species almost always result in unviable offspring. Even hybrids that were crossed with individuals from parent populations often had unviable offspring. This indicates that this species requires non-kin mating to survive, which may help with decreasing inbreeding events. Certain larvae did better in their home environments and struggled in foreign environments, indicating potential local adaptation. There were also slight coloration changes between males in Massachusetts (a "warm leathery tone") and males in South Dakota (a "chestnut brown" color), indicating potential genetic differences between the two populations, which are separated by unsuitable habitat and by a distance of 2000 miles (3218.688&nbsp;km). However, due to the age of the study, more work is needed to confirm that local adaptation is indeed taking place in North American populations of small pearl-bordered fritillaries instead of individual plasticity.

Another study found Boloria selene are quite plastic in their response to temperature variation, and will adjust much of their life cycle in response to temperature changes such as an earlier warming that comes with an early spring. The same study also analyzed among and between population data, and suggested that these animals quickly capitalize on early warming and late cooling regardless of location (in the US at least), and seem to also know when to wait longer or shorter before beginning reproduction.