Beautiful butterflies
Butterflies are arguably our most popular insects. Their colourful, fluttering forms often raise a smile on spring and summer days. Hampstead Heath is a great place to find many of them, with 28 species recorded here.
Butterflies belong to the insect order Lepidoptera, along with moths. The order name means ‘tiled wing’, after the microscopic scales that cover their wings. These provide the insect’s colour patterns, either through ‘true colour’ pigments or ‘structural colour’ via the refraction of light by the scales, lending an iridescent sheen. The differences between butterflies and moths are more subtle than colour and require a closer look- some butterflies are dull-coloured, whilst some moths are colourful and fly during the day! The easiest clue is their antennae. Unlike moths, Butterflies have clubbed antennae. Technically specking though, butterflies are a just a group of moths!
Brimstone Gonepteryx rhamni © Jo Maddox
One of the first butterflies out is the Brimstone, a bright yellow herald of spring emerging from winter refuges as early as February. They are soon followed by Peacock butterflies, with their namesake eye spots and Small tortoiseshells, which overwinter in hollow trees, log piles, sheds and other sheltered nooks.
The ragged-looking Comma butterfly camouflages amongst dead leaves in winter. These are the exceptions, as most species sit out the cool winter as pupae, emerging as adults in warmer weather. Some butterflies are summer migrants to Britain, such as Red admirals and Painted ladies. It’s amazing to think of these fragile insects crossing the channel!
Comma Polygonia c-album
When it comes to caterpillar foodplants, butterflies are fussy eaters. The ‘whites’ tend towards the mustard family, including the ‘cabbage whites’ infamous to gardeners (actually two species- The Large white and Small white). The striking orange and black Nymphalids (Peacocks, Tortoiseshells, Commas and Red admiral) mostly target nettles, whilst the ‘Browns’ e.g. Meadow brown, Gatekeeper and Speckled Wood feed on tall grasses- a good reason to leave areas uncut! Others take to the trees, such as the small Hairstreak butterflies which live in the canopy, and the impressive Purple emperor. This ‘imperial majesty’ of butterflies can be seen on Sandy Heath, where the spectacular iridescent purple males patrol willow stands to court females.
Gatekeeper Pyronia tithonus
Common Blue Polyomattus icarus
Butterflies can identify their foodplants by scent, honing in with their antennae, then using chemical receptors on their feet to find a suitable leaf, stem or flower to lay their eggs. Upon hatching, the begin their main mission- eating! They pile on the pounds (or grams) and build up fat reserves to develop into strong adults. As they grow rapidly, they must shed their skin four times until they are fully grown, usually within a month. They then seek a place to pupate, secure themselves with a line of silk and shed their skin a final time into a chrysalis.
This is when the magic of metamorphosis happens. Inside the chrysalis, the caterpillar’s body breaks down into a cellular soup save for essential organs such as their breathing tubes and nervous system. Hormones reorganise and activate the division of cells to form wings and other butterfly body parts. Eventually, the butterfly hatches out, pumps up its wings, dries off and takes flight.
Peacock caterpillars Aglais io munching on nettles in South Meadow. © Rory Dimond
Now equipped with a long, straw-like proboscis, the adult butterflies mostly sup on sugary nectar to fuel their flight, helping to pollinate flowers in the process. They will also feed from sap runs, rotting fruit and honeydew (the sugary waste from aphids), but seek other nutrients and minerals from more unsavoury places, including dung and wet mud. They now focus on reproduction, with their bright colours likely helping to recognise and court a mate. Although butterflies may seem benign, the males of some species are territorial, chasing potential rivals and engaging in wing-clattering fights. This can result in some very battered-looking butterflies late in the season! Some butterflies will produce several broods a year, so flushes of fresh individuals can appear at different times.
Being active and colourful makes butterflies easy to spot on a sunny walk, and easy to survey too. Heath Hands has a butterfly monitoring programme, providing information to City of London Ecologists to inform how the Heath’s habitats are managed, as well as feeding into Butterfly Conservation’s National Butterfly Monitoring Scheme. Butterfly Conservation are also running their annual ‘Big Butterfly Count’ from the 16th July to the 8th August. Anyone can take part from their gardens or local greenspaces, to help build a picture of how butterflies are doing across the nation. See the website for details.
Knowing the fortunes of butterflies is important, as unfortunately most of our species have declined in both rural and urban areas, due to the loss of breeding habitat and the use of pesticides and herbicides. We are lucky to have brilliant habitat for butterflies on Hampstead Heath, with a patchwork of meadows, grasslands, hedgerows and scrubby areas where they can feed and breed. We hope you enjoy spotting these beautiful insects this summer.
If you would like to get involved with our wildlife surveys, you can find out more here and if you’d like to find out more about butterflies on the Heath, check out our upcoming butterfly walk with a London butterfly expert.
Purple emperor © Bernard du Pont. The only photo in the article not taken on Hampstead Heath.
