New Forest Butterflies

Over a century ago the New Forest was the richest area in the country for butterflies supporting a large number of woodland, heathland and grassland species. However, changes in woodland management (particularly the lack of coppicing) and more intensive grazing by ponies, cattle and deer destroyed a significant amount of butterfly habitat by removing the herb and wild flower layer which is so crucial to the survival of many species.

The Victorians and Edwardians were keen butterfly admirers and collectors who used to flock to the New Forest to marvel at the summer displays of these beautiful creatures and sketch them. One of the most prominent butterfly experts and collectors of this era was Frederick William Frohawk (1861-1946). Frohawk was a prominent zoological artist and lepidopterist who made numerous visits to the New Forest, including spending his honeymoon there. His book, Natural History of British Butterflies (1924), is still regarded by many as the definitive work on the subject.

FrohawkIn one of his articles about the silver washed fritillary in the New Forest, he wrote: “It used to occur in such profusion that it was usual to see 40 to 50 of these fine insects assembled on a large bramble bush. They were so common that, as the sun touched their overnight resting places, they dropped from the trees like an autumnal shower of falling leaves”. Unfortunately, such has been the decline in butterfly populations that it is unlikely that anyone alive today has witnessed such a sight. Frowhawk named his daughter Valenzina after the dark green form of the silver washed fritillary which can also been seen in the New Forest. In 1996 Valenzina inaugurated a commemorative sign marking the “Frohawk Ride” in Parkhill Inclosure in memory of her father.

In 2011, a survey by Butterfly Conservation reported that 75% of UK butterflies showed a 10-year decrease in either their distribution or population levels. For many years butterflies have been regarded as excellent indicators of the state of health of an environment. As a result of their high reproductive rates, short life cycles and their low level in the food chain they respond rapidly to any change in their habitat which, in turn, provides an early warning system for other reductions in wildlife. In particular, birds plan their whole breeding season around when caterpillars will be most abundant. If the butterfly and resultant caterpillar numbers are depleted then there’s a knock-on effect in the availability of food for developing chicks in their nests. Butterflies are also good plant pollinators.

There are many reasons for this decline in butterfly numbers but these fall largely into two categories – climate change and loss of habitat. Whilst it is difficult to control the weather, habitat loss has arisen as a result of industrial farming and over grazing with resultant loss in nectar plants and hedgerows, plus a lack of intensive woodland management such as coppicing.

However, butterflies are egg machines and they don’t need a lot of hot weather to get the population back up, providing that they have the correct habitat. Nowadays, the Forestry Commission is working to improve neglected butterfly habitat. During the Autumn and Winter months conservation work is undertaken by volunteers, under the direction of the New Forest Keepers, to create butterfly corridors by opening up ride edges to create more light on the forest floor. By doing this, seeds that have lain dormant for years start to germinate with flowers such as Bugle and Violet re-appearing providing a food source that some species cannot survive without. This work is undertaken with input from Butterfly Conservation and is proving successful with species beginning to re-colonise, including the rare Pearl Bordered Fritillary. The New Forest is now home to 55% of the UK’s butterfly species.

The butterfly goes through four distinct stages – egg, caterpillar (lava), chrysalis (pupa) and, finally a butterfly.  Butterflies in their adult stage can live from a week to nearly a year depending on the species. Many species have long larval life stages while others can remain dormant in their pupal or egg stages. Several species of butterfly hibernate as adults during the cold winter months  while others  survive the winter as eggs, caterpillars or  chrysalis. If butterflies emerge early from hibernation, they may die  especially if it goes cold again and they are unable to locate  a suitable sheltered place to go back into hibernation. Species that hibernate as adults include  Red  Admiral, Painted Lady, Peacock, Small  Tortoiseshell, Comma and Brimstone. These need cold dry conditions to hibernate successfully although with warmer winters some can occasionally be seen on the wing in mid winter. In any event, it is these over wintering adults that are first on the wing each Spring and many species have more than one main flight period as new broods emerge later in Summer – April to September is the main butterfly viewing period. As butterflies age, their colour fades and the wings become ragged.

New Forest Butterflies
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Whilst most species are found on the ride edges inside Forest inclosures, some such as the Silver Studded Blue, Grayling and Dark Green Fritillary are more likely to be seen on the heaths. Many species of butterfly maintain territories and actively chase other species or individuals that may stray into them. The flight styles of different species of butterfly are often characteristic and some species have courtship flight displays.

The following chart is a rough guide to flight periods for different species although seasonal variations often occur dependent upon weather conditions. Butterflies are cold-blooded, which means that their body temperatures are not regulated on their own. A butterfly’s body temperature is instead affected by the temperatures of its surroundings. If it is too cold butterflies must warm up their bodies in order fly, if it is too warm they must cool down their bodies in order to fly. The optimum body temperature for a butterfly to fly is around 30°C. They can fly at lower temperatures but must regulate their body temperature and keep it warm by shivering their wings or basking in the sun. If it becomes too hot, the butterfly body temperature may become to warm to fly and it may have to cool its body temperature.

Butterfly-Chart

Periods marked in red are generally the peak flight period for each species with those marked orange indicating periods when they begin to emerge or start to disappear – the further from the red sector, the rarer their sightings should become.