As summer gives way to autumn, Dr Terry Mabbett reflects on the benefits of the passing season for British butterflies, with an abundance of nectar and food plants for the larvae, and warm temperatures promoting fast insect growth.
IT may be difficult to believe but butterflies of one species or another can be seen on the wing in every month of the year, despite most people regarding British butterflies as a summertime experience.
Most species have several broods per season starting as early as spring and extending through into autumn, which means there are insects at all stages of development throughout the season. But the enduring picture is still of butterflies imbibing nectar from summer flowers, although some of the most frequently visited plant species are not native to the British Isles.
READ MORE: Butterflies on the wing in spring
Buddleia davidii, introduced from China as an ornamental in the 19th century, and sometimes called summer lilac, is the classic case in point. Despite the more recent graduation of Buddleia davidii into an invasive weed species, the flowering shrub is so attractive to common butterflies, including peacock, small tortoiseshell and red admiral, to have been called the ‘butterfly bush’.
Some of the nectar plants most favoured by butterflies are also classified as invasive and injurious weeds, which is something arborists and landscapers charged with clearing land should bear in mind.
The herbaceous creeping thistle or woody shrubs like buddleia or bramble may look unsightly and compete with young trees, but their presence is the reason why butterflies will be fluttering around while the arborist is toiling. A balance has to be struck, especially for ragwort which is toxic when ingested by animals. Clearing sites of all vegetation, either mechanically or using herbicide, is not a good idea if you want to encourage a range of butterflies.
PAINTED LADY (VANESSA CARDUI) – FAMILY NYMPHALIDAE, SUB-GROUP NYMPHALINAE (THE ‘NYMPALIDS’ OR ‘VANESSIDS’)
All butterflies are beautiful, but some are more beautiful than others. Common names invariably tell the observer a great deal about a butterfly species’ position in the beauty stakes. Painted lady, peacock and red admiral are names which go that extra mile in the beauty stakes of British butterflies.
The appearance of the painted lady in late spring/early summer is one of the most memorable spectacles of the season, especially since these beautiful but delicate creatures will have winged it all the way from the desert fringes of North Africa to get here. But this North Africa–British Isles butterfly bubble belies a near global distribution of the painted lady, nicknamed the ‘cosmopolitan butterfly’ precisely because it is the most widely spread species in the world.
Despite arriving here from much warmer climes, painted lady butterflies are found feeding and breeding the length and breadth of Britain during the summer months, although numbers do vary greatly from year to year. Exactly 100 years ago Richard South, who described the painted lady as a ‘notorious migrant’, said movement from its ‘proper home’ in North Africa is determined by population pressures and is caused by an innate interest in securing future generations of the species. Whatever the reason for leaving North Africa, it does so in numbers and style.
The migration route is similar to the red admiral (Vanessa atalanta), also arriving in large numbers from southern Europe and North Africa in late spring and early summer. However, unlike red admiral which now overwinters to an extent in southern England, any evidence for overwintering by the painted lady in England is tenuous to say the least.
However, Howard M. Frost says painted lady can successfully overwinter in the European Mediterranean area. And even further north including southern England as observed in Cornwall during the winter of 1997/98. Be that as it may, the UK summer population is still dependent on an annual build-up of adult butterflies from North Africa, says Frost. He cites 1996 as the largest immigration for 300 years with many millions arriving nationally including 50,000 in Yorkshire.
In modern ‘lepidopteran lingo’ the painted lady is described as a ‘polyvoltine’ species resident in North Africa. Polyvoltine means having several broods a year, which the painted lady certainly achieves in Britain. After arriving from North Africa in May/June at least two broods are accomplished (July/August and September/October) with numbers peaking from July to September. In good years, especially in southern England, a much smaller third generation may be squeezed in with butterflies out and about in November.
Prominently ribbed eggs, green at first but darker with age, are laid one per leaf on specific food plants. Thistles like the exotic and often invasive Carduus species, and the native and highly invasive Cirsium species, are the preferred food plants in Britain and Ireland.
READ MORE: Building up plant biodiversity to support butterflies
However, a range of other wild and cultivated plant species including mallows (Malva species), burdock (Arctium species), Viper’s Bugloss (Echium vulgare) and even common nettle (Urtica dioica) have also been recorded as food plants. And this is another example of primary and preferred food plants, in this instance the thistles, regarded as weeds and often uprooted and cleared without their importance for butterfly biodiversity being appreciated or understood.
The larvae are relatively short and distinctly stout with a bristly body of variable ground colour (grey-green and ochreous-grey to blackish) and topped with a dark-coloured head. The larval period begins by fixing up the leaf margins to form a type of pocket for concealment but larvae gradually reveal themselves as they consume the fleshy part of the leaf. Transformation into the grey or greenish chrysalis, shaded or striped with brown markings, is carried out in a similar leaf pocket structure.
The adult butterfly takes four weeks to complete the life cycle; fast by British butterfly standards. Like most other butterflies, underwing colouration does not come up to the upperwings’ splendour. However, relative underwing drabness provides excellent camouflage against predators when painted lady is resting on the ground with its wings closed.
Upperwing patterns and colouration can vary but the usual colour of newly emerged specimens is tawny-orange with a tinge of pink or a rosy flush with black markings and white spots at the tips of the forewings. Hind wings have rows of black spots.
Given its worldwide distribution, Vanessa cardui can clearly nectar on a huge range of flowering plants, but in the British Isles thistles are the most frequented in the wider environment and buddleia in parks and gardens.
British-born painted lady butterflies make the return trip to North Africa in autumn. The is no current concern about its conservation status, but negative impacts of climate warming on the species’ North African homeland could be a cause for future concern.
SMALL TORTOISESHELL (AGLAIS URTICAE) – FAMILY NYMPHALIDAE, SUB-GROUP NYMPHALINAE (THE ‘NYMPALIDS’ OR ‘VANESSIDS’)
Together with red admiral, painted lady and other related species, the small tortoiseshell is called a ‘vanessid’ butterfly, derived from the name ‘Vanessa’ with all sorts of mythological origins. The most likely (and attractive) is reference to the mystic Ancient Greek goddess Phanessa who as Pandora’s daughter had a fascination for butterflies.
Red admiral and painted lady butterflies carry out long distance migration between North Africa and Britain (and vice versa), while small tortoiseshells, in the main, are resident in the British Isles for 12 months of the year. However, this highly mobile species does show some shorter migration from continental Europe into Britain and from the south of England northwards into the rest of the British Isles. This can be mistaken for local emergence, says Frost.
‘Aglaia’ from which Linnaeus derived the genus name (Aglais) was one of the three sister goddesses and givers of charm and beauty in Greek mythology. ‘Aglais’ was clearly bestowed to reflect the elegance of this butterfly. The name tortoiseshell may well suit the intricate pattern of dull colours on the underwing surface, but it definitely belies the colour and beauty of the upperwing surface.
This resident species overwinters as the adult butterfly and emerges from hibernation in March to May. Small tortoiseshell completes one to three broods from late spring and into autumn and is traditionally regarded as our most ubiquitous butterfly.
Like other vanessid butterflies, including comma, peacock and red admiral, Aglais urticae as the species name shows it is critically dependent on common stinging nettle (Urtica dioica) and the small stinging nettle (Urtica urens). These nettles are the larval food plants although female butterflies will not lay their eggs on any old bed of nettles. The ideal site is a large bed of nettles in a sunny position which have been cut to encourage new growth.
Eggs are laid in clusters on the underside of a terminal leaf during May (first brood) and again in July (second brood). There may be a much smaller third brood.
According to Frost, the number of generations produced appears to be controlled by the timing of emergence. Apparently describing the situation in Yorkshire, he says butterflies emerging from the second brood by the first week of August are able to produce another generation, but those emerging after this time may not be reproductive. As such they may go into hibernation or drift southwards, searching for suitable hibernating sites and drinking nectar on the way to build up lipid reserves ready for hibernation.
Because eggs are laid in clusters, hatching larvae are initially gregarious and usually so until the last instar stage when they disperse and live independently prior to pupation. Final instar stage larva is yellowish in colour closely covered with black speckling and short hairs and with a black band down the centre of the back. It pupates into a grey-coloured chrysalis which is sometimes tinged with pink.
Small tortoiseshell is one of the small group of British resident butterflies which overwinter in the adult butterfly stage and is notorious for going into hibernation late and coming out early in response to unseasonably warm winter conditions. Richard South (1921) described how small tortoiseshell butterflies were seen as early as January and February in 1896 and as late as December at other times in the 19th century. Once the weather starts to cool down in autumn small tortoiseshell butterflies will start to look for somewhere warm to hibernate.
Problems arise when butterflies select houses for winter hibernation because the homes invariably become too warm for their own good. Butterflies may fly inside during late summer but are unable to get out in spring. Or the butterflies may wake up in mid-winter when it is not warm enough outside for them to survive. Butterflies including small tortoiseshell which enter homes should not be released outside in winter because they will not survive. Instead, they should be removed to a protected but cool building like a garage, barn or shed where they can resume their hibernation periods.
SMALL COPPER (LYCAENA PHLAEAS) – FAMILY LYCAENIDAE, SUB-GROUP LYCAENINAE (THE COPPERS)
Small copper is not as large nor as flashy as the painted lady or red admiral but compensates in other ways. Not for nothing did early lepidopterists call this species the ‘smart’ butterfly. It is highly active and indulges in acrobatics, while a comparatively less complicated colouration offers observers the beauty of simplicity.
Ground colour on the forewings is rich copper banded by walnut-brown margins with black markings on the copper-coloured areas. This colour scheme is essentially reversed for the hindwings which are walnut-brown with copper-coloured margins carrying black marks, and an altogether more geometric pattern but all the more pleasing for it. However, wide variations in colour have been recorded by lepidopterists over the centuries including ‘alba’, a rare form described by Richard South (1921). Ground colour on the forewings and outer band on the hindwings is not ‘burnished copper’ but silvery white. Looking at the colour plate in South’s book (The Butterflies of the British Isles) this extreme variation from the small copper ‘norm’ could completely confuse and throw the unseasoned observer.
White eggs are laid on the undersides of leaves of select Rumex species (docks and sorrels). The slug-like larva pupates after 25–30 days into a chrysalis resembling a dumpy sac suspended from the plant by silken pads. There are two to three broods per season with later hatching larvae overwintering in this same larva stage. They may continue to feed during mild winter spells but become dormant during cold spells, eventually feeding more actively and sustainably in March. They pupate later in March and emerge as butterflies starting in early May.
Small copper was always credited with a relatively restricted range of food plants although current observations and records indicate it may be more restricted than first thought. Texts going back a century or more list a wider range of Rumex species as food plants, but more recent records indicate primary food plants as sorrels of which sheep’s sorrel (Rumex acetosella), with characteristic arrow-head leaves, is most favoured.
Like other members of the plant family Polygonaceae, sheep’s sorrel contains high levels of oxalic acid which gives these plants their acid-lemon flavour. The specific name ‘acetosella’ is derived from the Latin ‘acetum’ (meaning vinegar) and testimony to a sour, sharp taste of the leaves.
Sheep’s sorrel is essentially an acidophilic weed plant which ties in with my highly localised sightings of the butterfly on the fringes of North London. Classic wet acid grassland is rare in and around North London but there is an isolated oasis on Hadley Green and the neighbouring Old Fold Manor golf course. Hadley Green is where I have been able to photograph small copper butterflies nectaring on swathes of creeping thistles still flowering in August.
However, the main interest for the small coppers I saw was not the creeping thistle, but almost certainly the sheep’s sorrel growing in profusion amongst the rough grasses along with the equally acidophilic field woodrush. Neither sheep’s sorrel nor field woodrush are found frequently if at all elsewhere in the area.
Frost in his The Butterflies of Yorkshire alludes to the small copper’s affinity for sheep’s sorrel as the larval food plant, and how the practice of burning heather moorland appears particularly beneficial because it promotes the growth of sheep’s sorrel as a colonising species of bare ground. This type of land management generates patches of new growth in an open, sunlit position, perfect for both sheep’s sorrel and the small copper butterfly. Sheep’s sorrel is a sun-loving plant quickly shaded out by regenerating tree and shrub growth. He also highlights the increasing importance of brownfield sites for the small copper and goes on to emphasise the importance of periodic land disturbance for this species because its food plants are among the first to colonise patches of bare soil.
However, there is something on the horizon which could have a major and devastating effect on the small copper and indeed other species of butterfly with similar habitat preferences and requirements. Looming is the wholesale removal of millions of hectares of rough grazing grassland on acid reaction soils from sheep production into tree planting, as part of the government’s move towards net-zero carbon emissions.
LONG-LOST LARGE COPPER (LYCAENA DISPAR DISPAR)
Anyone who thinks such a seismic change in land use and management will not impact the small copper (and many other species) needs to study the rise, fall and fate of the closely related large copper butterfly, discovered near Spalding in Lincolnshire in 1749 but extinct by 1851.
The demise of the large copper was apparently due to major changes in land use and management, in this case draining of marshland mainly for arable farming and especially in the Fens. Redemption could be on the horizon with planned restoration of peatlands. However, we can’t retrieve our true native large copper Lycaena dispar dispar which is gone forever. As in previous attempts, any restoration of the large copper butterfly in the UK will have to use Lycaena dispar batavus, which is still found in the Netherlands.
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