We have recently had a spell of nice warm weather which brought out some of our native butterflies to feed on the buddleia and lavender which has been planted around the centre, not only for butterflies but also for the bumble bees.
The three species of butterfly we have seen here at SOS this year are the Red Admiral, the Small Tortoiseshell and the Large White - this despite the prolonged rain through the spring and summer, which hit our native butterflies very hard.
The Red Admiral Butterfly is a frequent visitor to gardens throughout the British Isles and one of our most well-known butterflies. This butterfly is unmistakable, with the velvety black wings intersected by striking red bands.
This butterfly is primarily a migrant to our shores but due to domestic sightings of individuals in the first few months of the year, especially in the south of England, it now is considered by some to be resident, albeit representing only a small fraction of the UK Red Admiral population. This gets topped up every year with migrants arriving in May and June from central Europe. though the majority of these are unable to survive our winter, especially in the cooler regions of the British Isles.
The Small Tortoiseshell Butterfly is another of our most familiar species, appearing in gardens throughout the British Isles. However, this species has suffered a worrying decline over the last few years, especially in the south.
This butterfly has always fluctuated in numbers, but the cause of the most-recent decline is not yet known, although various theories have been proposed. One is the increasing presence of a particular parasitic fly, sturmia bella, due to global warming.
The fly lays its eggs on leaves of the food plant, close to where butterfly larvae are feeding: these eat the fly's eggs whole and the grubs that emerge feed on the insides of their host, avoiding the vital organs. A fly grub eventually kills its host and emerges from either the fully-grown larva or pupa before itself pupating. Although the fly attacks related species, such as the Peacock and Red Admiral, it is believed that the lifecycle of the Small Tortoiseshell is better-synchronised with that of the fly and it is therefore more prone to parasitism
Finally, the Large White Butterfly (pieris brassicae) and the small white butterfly (pieris rapae) are commonly seen flying within our gardens and are affectionately called summer snowflakes.
While the Small White is a native species, the Large White usually migrates from southern Europe because they don't often survive a north European winter and have often been seen crossing the English channel in swarms of many hundred individuals to reach our shores.
The Large White's eggs are often laid in batches of 10 to 20 which hatch into yellow and black, slightly hairy caterpillars after about two weeks and feed for a month or more to reach a length of about 50mm before they turn into pupae.
The eggs of the Small White are laid singly and hatch into bright velvety-green caterpillars which burrow into the hearts of cabbages to feed. They leave their food plants when they're ready to pupate and usually attach themselves to a vertical surface such as a fence or wall with a silk girdle before they finally shed their skin in the summer months and hatch into the next generation of butterflies.
As all horticulturalists and gardeners are all too aware, both species of white butterfly can cause extensive damage to cabbages and other brassicas, eating holes in leaves and tunnelling into the hearts. The severity of cabbage white problems can vary considerably from year to year due to weather, immigration and diseases.