Glanville fritillary

In the UK the Glanville fritillary occurs only on soft undercliff and chine grassland and where its main larval food plant Plantago lanceolata (English plantain) occurs in abundance on sheltered, south facing slopes. The Glanville fritillary is a highly restricted species within the UK, being confined to the Isle of Wight and even there being largely limited to the southern coast.[12] It also occurs in the Channel Islands, and since 1990 there has been a mainland site on the Hampshire coast, possibly the result of an introduction. There are small introduced populations on the Somerset coast and two in Surrey: one near Wrecclesham, and one at a nature reserve in Addington, near Croydon.

Historic UK records suggest a distribution which went as far north as Lincolnshire. However, by the middle of the 19th century the Glanville fritillary was known only from the Isle of Wight and the coast of Kent between Folkestone and Sandwich. It became extinct in Kent by the mid-1860s.

Ribwort plantain

After hatching, Glanville fritillary caterpillars live in gregarious sibling groups. They feed on their host plant, either Plantoago lanceolata (ribwort plantain) or Veronica spicata (spiked speedwell). Adult females prefer one plant over the other when choosing where to lay their eggs, but the larvae do not have a feeding preference for either plant when they are born.[15]

Spiked speedwell

As an attempt to fend off predators and parasitoids, the spiked speedwell emits volatile organic compounds (VOCs) when threatened. Some researchers found that this plant species has two different defenses for when it is being fed on and when a butterfly is in oviposition. The oviposition of the butterfly on this plant was able to induce the increase of two ketones (6-methyl-5-hepten-2-one and t-geranylacetone) and the suppression of green leaf volatiles (GLVs).[16]

Adult Glanville fritillaries have a diet that consists solely of nectar. It has been shown that larvae with higher amounts of iridoid glycosides have better defense against parasitoids and bacterial pathogens.[17]

A female Glanville fritillary will lay as many as 10 clutches of eggs in her lifetime. These clutches can range in size from 50 up to 300 eggs and are laid on the underside of the larval food plant of either Plantago lanceolata (ribwort plantain) or Veronica spicata (spiked speedwell).[18] After hatching, the caterpillars feed on their host plants until the end of the summer where they spin a "winter nest" to diapause. When winter is over they emerge from their nest to feed again before pupating around the beginning of May. A month later, the adult fritillaries emerge and go about their adult lives of feeding, mating, and laying eggs.[18]

In the Glanville fritillary, clutch size is highly important as larval survival depends on groups size. Thus, understanding the different factors that contribute to clutch size is important in developing an understanding of population dynamics and life cycle.[19]

Clutch size is inversely related to the size of the clutches previously laid, meaning that the more eggs a female lays in years prior, the fewer eggs will be in the present clutch. Further, it is known that clutch sizes decrease with the age of the female. This is thought to be due to resource depletion over time in the female, potentially from high investment in earlier clutches.[19]

Clutch size also increases with increased intervals between oviposition. Typical Glanville fritillary oviposition occurs once every two days.

Glanville fritillary females vary in their PGI, a glycolytic enzyme, genotype. The genotype of the female influences the time of day that she is active, which also influence her ability to lay larger clutches. Heterozygote females are able to operate earlier in the day compared to all other genotypes. Further, females with a Pgi-f allele are able to begin oviposition earlier in the day and are also able to lay larger clutch sizes. The Pgi-f allele contributes to a higher metabolic rate and the ability for females to take advantage of the climate of the early day - both of which factors allow for increased clutch size.[19]

• 
  Caterpillar
• 
  Pupa
• 
  Imago

Glanville fritillary eggs and pupae are often parasitized by several species of parasitoids. Two specialist species:[20]

• Cotesia melitaearum
• Hyposoter horticola

And several generalist species:

• Pterolmalus apum.[21]
• Ichneumon gracilicornis
• Pteromalus apum
• Pteromalus puparum
• Coelopisthia caledonica[22]

And has several hyperparasitoids[22]

• Mesochorus stigmaticus (a specialist)
• Gelis agilis
• Gelis ruficornis
• Gelis acarorum

The parasitoid C. melitaearum can be extremely detrimental to Glanville fritillary populations if it is able to become well established. This species is able to increase its own parasitism if the fritillary population is also increasing in size and age, but will decrease if said population becomes isolated. Thus, in well established fritillary populations there is a risk of local extinction by the C. melitaearum parasitoid.[20]

Subspecies include:

• Melitaea cinxia cinxia
• Melitaea cinxia amardea Grum-Grshimailo, 1895
• Melitaea cinxia atlantis Le Cerf, 1928
• Melitaea cinxia clarissa Staudinger, 1901
• Melitaea cinxia heynei Rühl, 1895
• Melitaea cinxia karavajevi Obraztsov, 1936
• Melitaea cinxia oasis Huang & Murayama
• Melitaea cinxia sacarina Fruhstorfer, 1917
• Melitaea cinxia tschujaca Seitz, 1908

As the global temperature of the Earth warms each year, many butterfly species are forced to shift northward in order to keep living in their preferred climates. Scientists have found that migratory species, such as monarch butterflies, are better able to adapt to the rising temperatures than sedentary species, such as Glanville fritillaries.[5] Glanville fritillaries will migrate around the Åland Islands to different habitat patches, but they will not embark on great transcontinental seasonal migrations like other butterflies do.[6] Because of this they are very susceptible to climate change, which is something to keep in mind when considering plans to aid in the conservation of this species.

This butterfly is not currently listed as threatened in Europe, but its UK BAP status is Priority Species. The NERC act of England lists it as species of principal importance. Its Butterfly Conservation priority is high, so this is a butterfly likely to be increasingly threatened in the coming years.[23]