Butterflies are the most well-studied insects in the UK and they help to provide information on the health of wider insect communities that are more difficult to record. They are a welcome sight in UK gardens, in nature reserves and around sunny wild areas.
However, the small tortoiseshell butterfly is still facing a number of challenges, including:
The parasitic fly Sturmia bella lays its eggs on nettle leaves - the small tortoiseshell caterpillars eat the eggs, which kills the caterpillars.
Scientific name: Aglais urticae
Butterfly: mainly orange with yellow and black stripes on the fore wing with a distinctive white spot towards the outer edge, small blue crescents bordered by black arcs are visible on the margins of both the fore and hind wings, the under wings are a mixture of light and dark brown (providing excellent camouflage)
Ovum (egg): eggs are bright green and a few millimetres in diameter, laid in clumps of around 80 to 100 eggs on the underside of nettle leaves
Caterpillars: range in size from 1.25mm - 22.2mm (grow progressively larger through five life stages called ‘instars’), begin black in colour and progress to olive green and black with yellow stripes, bristles cover the body
Chrysalis: measures between 20mm – 22mm long and attaches to a suitably sheltered area via a hook with the head facing down, colour varies from dusky brown to pale yellow/green, slight chequered pattern with lateral ridges and small regular points
Sometimes confused with: large tortoiseshell butterfly, painted lady butterfly, comma butterfly
Small tortoiseshell butterflies can be found in a variety of habitats, and visit a range of wildflowers and plants commonly found in gardens including thistles, buddleia and red valerian.
The key food plants are common ‘stinging’ nettle and small nettle, therefore these plants are vital for successful reproduction.
During hibernation, these butterflies can sometimes be found in outbuildings, wood piles and hollows in trees. They may be found hibernating alone, or sometimes with other individuals.
Adults usually emerge from hibernation in March or early April, and are regularly seen flying in late summer. Mating occurs close to nettle patches, where the male creates a territory. When a female enters this area; courtship commences. This involves the male drumming his antennae on the female’s hind wings. A large proportion of courtship includes the pair basking in the sun. In the early evening, both female and male will move into vegetation where mating ensues.
Eggs are laid on the underside of nettle leaves and it takes between one and three weeks for the larvae to emerge. The larvae live communally, eating nettles and moving from plant to plant by building webs. The larvae move through five stages, shedding their skin and taking around 26 days to mature. Larvae then disperse to find a suitable site to pupate and once the chrysalis is formed, it takes from two to four weeks to emerge as a butterfly.