Marsh fritillary

The marsh fritillary (Euphydryas aurinia) is a butterfly of the family Nymphalidae. Commonly distributed in the Palearctic region, the marsh fritillary's common name derives from one of its several habitats, marshland. The prolonged larval stage lasts for approximately seven to eight months and includes a period of diapause over the winter. The larvae are dependent on the host food plant Succisa pratensis not only for feeding but also for hibernation, because silken webs are formed on the host plant as the gregarious larvae enter hibernation. Females lay eggs in batches on the host plant and are, like other batch-layers, selective about the location of oviposition because offspring survivorship levels for batch-layers are more tied to location selection than they are for single-egg layers.

As of 2019 the butterfly's global conservation status is considered of least concern, but it has faced rapid decline and is considered regionally vulnerable or endangered over much of its range.

Taxonomy

E. aurinia is represented by many subspecies. The most widely accepted are:

Euphydryas aurinia aurinia central Europe, southern Europe, western Siberia
Euphydryas aurinia bulgarica (Fruhstorfer, 1916) Carpathian Mountains
Euphydryas aurinia laeta (Christoph, 1893) central Siberia, Altai, Sayan, Transbaikal
Euphydryas aurinia beckeri (Lederer, 1853) Morocco (Middle Atlas, Rif Mountains) submarginal band of the hindwing is of a magnificent deep russet-red colour and nearly occupies the whole outer half of the wing, being outwardly bordered by black lunules centred with pale yellow
Euphydryas aurinia barraguei (Betz, 1956) Algeria
Euphydryas aurinia provincialis (Boisduval, 1828) (France and northern Italy)
Euphydryas aurinia debilis(Oberthür, 1909) Mountainous areas like Pyrenees and Alps

but the total number of described subspecies is much higher, especially in the eastern Palaearctic. The insect may be best considered a superspecies.

E.aurinia is in the subgenus Eurodryas The clade members are:

Euphydryas aurinia (Rottemburg, 1775)
Euphydryas provincialis (Boisduval, 1828)
Euphydryas orientalis (Herrich-Schäffer, 1851)
Euphydryas asiatica (Staudinger, 1881)
Euphydryas sibirica (Staudinger, 1871)
Euphydryas laeta (Christoph, 1893)
Euphydryas desfontainii (Godart, 1819)

Marsh fritillary (Euphydryas aurinia estonica).jpg|E. a. estonica, Estonia

(MHNT) Euphydryas aurinia beckeri - Calar Alto, Andalousie, Espagne - male dorsal.jpg| Euphydryas aurinia beckeri ♂

(MHNT) Euphydryas aurinia beckeri - Calar Alto, Andalousie, Espagne - male ventral.jpg|Euphydryas aurinia beckeri ♂ △

(MHNT) Euphydryas aurinia debilis - Pologne - male dorsal.jpg|E. a. debilis ♂

(MHNT) Euphydryas aurinia debilis - Pologne - male ventral.jpg| E. a. debilis ♂ △

(MHNT) Euphydryas aurinia provincialis - La Motte Var France - male dorsal.jpg|E. a. provincialis ♂

(MHNT) Euphydryas aurinia provincialis - La Motte Var France - male ventral.jpg|E. a. provincialis ♂ △

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Description

Euphydryas aurinia has a wingspan of in males. The females are usually larger than the males, with a wingspan of . These small butterflies are variable in markings and colouration, with many forms and subspecies. The adult butterflies usually show a chequered pattern of brown, orange, and yellow markings. Silver markings are present on the hindwing edge. The underside of the wings is patterned with yellow, orange, and brown without any silver colouration at all. The eggs are yellow, and easily identified because of the large batch size. The larvae are black.

File:Euphydryas aurinia MHNT CUT 2013 3 26 Clermont le Fort Dorsal.jpg|Dorsal side

File:Euphydryas aurinia MHNT CUT 2013 3 26 Clermont le Fort Ventral.jpg|Ventral side

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Distribution and habitat

This species is widespread in the Palearctic realm, from Ireland in the west to Yakutia in the east, and to north-west China and Mongolia in the south. The marsh fritillary is in decline in Europe and it is one of eleven butterflies covered by the United Kingdom Biodiversity Action Plan. Within the British Isles, it is more frequent in the south and west, but especially in Wales where there is a stronghold.

This species lives in calcareous grassland, in woodland clearings, in damp marshy areas (hence the common name), and in heathy grassland, dominated by tussock forming grasses, including purple moor and rush pastures. In Finland, E. aurinia has been shown to favor semi-permanent grasslands and impermanent clearcuts in the forest. Young clearcuts were preferred over old clearcuts due to the dense growth of vegetation in old clearcut forests. In the United Kingdom, two types of grasslands can be inhabited by E. aurinia: damp grasslands that are either neutral or acidophilus and dry grasslands that have an abundance of plants growing in lime-rich soil (calcicolous grasslands). These butterflies can reach an elevation of above sea level. In 2018, a breeding population was found in Carmarthenshire, Wales, after an absence of 50 years.

In Lithuania (included into the Lithuanian Red Data Book since 2000, red list category-3 (R))(Rašomavičius, 2007) is protected insect species. Euphydryas aurinia usually is found in natural and seminatural moist or wet oligotrophic grasslands (purple moorgrass and heath rush meadows), base rich fens, mostly in Eastern, North-Western and Central Lithuania, where its main foodplant Succisa pratensis (Dipsacaceae) is abundant. Inhabited patches frequently are situated along woodland edges or surrounded by bushes. Species is not found in Southern Lithuania where sandy soils predominate and in South-Western Lithuania where agriculture is very intensive.

In Croatia, it is only present in the north, and even those findings are only historical. Attempts to confirm its presence have failed, but northern Ivanščica and the Lobor valley are considered promising.

Factors for optimal habitat

The availability of larval food plant S. pratensis and grass height are the most important factors in providing an optimal habitat for E. aurinia.

Host plant availability

Because caterpillars live in communal webs formed around their host plant and hibernate through the winter inside the web, the density of host plant is a crucial factor in forming the habitat of E. aurinia. Studies have shown that the density of host plant is directly correlated to the number of larval webs found, which in turn is directly related to the number of adult butterflies. Therefore, a habitat suitable for the larvae can indirectly influence the proliferation of adult butterflies.

Adult feeding

Adult butterflies feed on nectar opportunistically, so the density of host plant S. pratensis does not affect adult butterfly feeding. In fact, by the time adult butterflies emerge, S. pratensis does not even flower. They have also been observed feeding on Caltha palustris, also known as kingcup or marsh-marigold, and Ajuga reptans, also known as bugle or bugleweed.

Parental care

Oviposition discrimination

E. aurinia females are batch-layers, meaning they lay a large number of eggs at one site. Because 200–300 eggs are at stake every time an egg-laying site is chosen, batch-laying females tend to undergo a discrimination phase in searching for a location to lay eggs on. Each plant can serve as an egg-laying site for four to five clusters of eggs, meaning that more than a thousand larvae may hatch on a single plant. If so, the newly hatched larvae will face serious food shortage and fierce competition for food, which has huge repercussions for offspring survivorship. Therefore, Euphydryas and other batch-laying females, such as Melitaeini females, spend more time choosing a place to lay eggs and are more selective when looking for a host plant.

Size of host plant and vegetation density

Female oviposition depends largely on the size of host plant as well as density of vegetation cover. Studies have shown that females prefer to lay eggs on large host plants as opposed to smaller plants. This is to prevent food shortage and starvation of the larvae. Also, sparse, open vegetation structure is favored over dense, thick grasslands when the host plant S. pratensis is used for oviposition. The presence of a tall non-host plant (e.g. Deschampsia caespitosa) is negatively correlated with egg nests. Therefore, abandoned meadows with lime-rich soil have been identified as oviposition sites. Often, E. aurinia will lay eggs at edges of such meadows because the vegetation structure and plant height fit the female butterfly preference for oviposition.

Color of host plant

Females prefer to lay eggs on leaves with the highest chlorophyll contents. Therefore, the reflectance and chlorophyll concentration of leaves also affects the choice of oviposition site for E. aurinia. Chlorophyll content (the "greenness" of plants) can be an indicator for increased fitness of the host plant, which in turn will provide optimal growth opportunities for the newly hatched larvae. Females therefore use visual cues to seek out the greenest leaves to lay their eggs on. However, there are also indications that it is not high chlorophyll concentration but the presence of conspecific egg clusters which attracts females to oviposit on a certain leaf. During this time, they change color from brown to black.

thumb|200px|Pupa

Pupa

At the end of the sixth instar, pupae start forming. This occurs in the spring, around the end of March or beginning of April. Adults have short life spans, usually lasting about two weeks. Thus, the fluctuation of one habitat patch population size is unlikely to affect the population size of another habitat patch. The relative turnover rate of extinction and recolonization of previously empty habitat patches is high for E. aurinia, which indicates that extinction of one local population can be balanced by re-colonization of another. Such classic metapopulation characteristics explain why there is greater within-population genetic structuring in E. aurinia. Adult males display sedentary behavior, perching on bushes or grass. They observe and seek out females. Females mate once in their short lifetime and lay multiple batches of eggs.

Marsh fritillaries (Euphydryas aurinia) courting.jpg|Courting

Marsh fritillaries (Euphydryas aurinia) mating.jpg|Mating

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Enemies

Known predators of E. aurinia are cuckoos, frogs, and toads, and the ground beetle Pterostichus versicolor. All of these predators prey on the larvae. The parasitoid displays gregarious parasitoid larval behavior, meaning more than one parasitoid progeny can develop fully in or on the host. In fact, three regular generations of A. bignelli occur in one generation of E. aurinia, usually between the pupae, adult, and egg stages of the host. Also, parasitoid oviposition behavior is selective, meaning that A. bignelli is a specialist parasitoid. The percent of host population parasitized varies greatly, ranging from 0 to 80%. Thus, E. aurinia serves as a good indicator of environmental changes due to its vulnerability to habitat changes.

Habitat loss

thumb|Short film on the Marsh Fritillary by [[Natural Resources Wales]]

As of 2017, rapid decline of the population had been observed in Denmark due to loss of habitat and host plants.

As of 2019 the butterfly had become regionally extinct over much of its former range in the UK.