Watching dozens or even hundreds of butterflies flitting around a meadow full of brightly-coloured native flowers swishing in the breeze is an experience to be savoured but unfortunately it is much more likely to be experienced in Spain, France or Switzerland than Britain these days owing to the wholesale elimination of our flower meadows in the last hundred years. The level of destruction is about 97 per cent.
This is a matter of broader concern because the survival or otherwise of Lepidoptera in general, and butterflies in particular, is a litmus test for the whole of the invertebrate animal kingdom. Butterflies are unique among invertebrates in being known in every case, and even by experts, according to the English name, not the scientific one. Even dragonflies cannot quite match that.
This usage is an index partly of numbers and distinct, identifiable differences between the nearly 60 resident species - try giving an English name to the 67 mining bees from the Andrena family, and telling them apart without a microscope.
Butterflies are ensconced in popular culture. People are well disposed towards them, perhaps partly because they are not predators but surely mainly because they are colourful and lively, because they represent brightness, summer, sunshine, the open air. A solitary wasp could represent all these in fact, but never in the minds of the public at large. So if we cannot protect our butterflies, what hope is there for the rest?
The same can be said for moths, given their greater number and the greater part they play in the food chain and breeding cycle as prey for wasps, birds, bats and various other small mammals. Incredibly, 75 species of larger moths decreased by more than 70 per cent nationally in the period 1968 to 2002, with the bulk of the declines in the south. The consequences of those losses are likely to be formidable.
Some unimproved grassland with flowers still exists, while some is being created or regenerated, and such downland sites as Pewsey Downs in Wiltshire, Martin Down in Hampshire and Denbies Hillside on Ranmore Common in Surrey provide some of the best locations for seeing the exceptional variety of species.
Three of those found on downland are priority species in the UK Bioversity Action Plan and two are species of conservation concern, which gives an indication of the knife edge on which they are balancing even with a number of safe sites.
The problem is exacerbated by uncertainty about exactly why populations of different butterflies crash or increase. Habitat destruction is an obvious cause, with its insidious effects perhaps intensified by such factors as an inability to disperse to form new colonies, and large fluctuations in breeding success for no apparent reason year on year. But there may be other considerations, including regional climatic variations, which remain mysterious despite all the scientific study put in.
The Marsh Fritillary (Eurodryas aurinia, wingspan 45mm) is much stronger in the west than the east of Britain. It inhabits damp meadows as well as dry downland and the caterpillars feed on Devil's Bit Scabious (Succisa pratensis), a pretty common plant. Sadly the same cannot be said for the Marsh Fritillary, which is declining in most of Europe.
The UK is now a stronghold for the species, though the term is only relative given that the butterfly's range has reduced by 62 per cent here in the last 150 years, with colonies disappearing at more than ten per cent per decade. The reasons for this are not crystal clear, though Butterfly Conservation, always at the forefront of protecting Lepidoptera in the UK, notes that "Its populations are highly volatile and the species probably requires extensive habitats or habitat networks for its long-term survival."
A fritillary which is not exactly under threat but which has undergone an inexplicable decline in certain parts of southern and eastern England is the Dark Green Fritillary (Argynnis aglaja, wingspan 66mm). The species uses Common Dog-violet (Viola riviniana) as the foodplant and is suited by flower-rich meadows, which it patrols at high speed in July and August.
Happily the situation with the Adonis Blue (Lysandra bellargus, wingspan 35mm), the brightest of all the blues, is better than with the Marsh Fritillary. Although it has experienced a decline throughout its range there are a number of stable and numerically strong sites, with expansion in Wiltshire and Dorset. Adonis Blues also benefit from having two broods each year, from mid-May to mid-June and early August to mid-September.
The requirements are short turf containing the foodplant Horseshoe Vetch (Hippocrepis comosa), plus ants to tend the larvae and pupae. Grazing by rabbits, cattle, and ponies or sheep (probably the most suitable on downland) can help provide this habitat. Applying rotational grazing allows species which need a longer sward a chance.
For grazing, Exmoor ponies are first-rate because they are tough, able to deal with slopes and stand no nonsense from people. They also deposit dung, which attracts one species above all others - males of the Chalkhill Blue (Lysandra coridon, wingspan 38mm), which is larger than all the British blues except the Large Blue and is a species of conservation concern. The adults are seen in August and, like the Adonis Blue, the caterpillars feed on Horseshoe Vetch.
The Silver-spotted Skipper (Hesperia comma, wingspan 30mm) is unmistakable in markings and behaviour, since it is active, basking and flying rapidly just above the ground, only when the temperature is 19C or higher. The foodplant, as with most Skippers, is a grass, in this case Sheep's-fescue (Festuca ovina). The butterfly, seen in August, breeds solely where this grass grows as small tufts in short or broken turf.
Two other kinds of Skipper which are more numerous and seen in May and/or June, occupying varied habitats including downland, are the Dingy Skipper (Erynnis tages, wingspan 29mm) and the Grizzled Skipper (Pyrgus malvae, wingspan 27mm).
Neither species feeds on grasses, respectively using Birdsfoot Trefoil (Lotus corniculatus) and Wild Strawberry (Fragaria vesca) or Creeping Cinquefoil (Potentilla repens). They are found in sunny, sheltered places.
The Duke of Burgundy (Hamearis lucina, wingspan 30mm) feeds on Cowslips (Primula veris) or Primroses (Primula vulgaris) but despite the presence of those plants in many areas the species has undergone a serious decline in the last 30 years, particularly in woodland, which seemingly leaves downland as its best hope.
The Duke of Burgundy is a species of conservation concern and it will be no surprise if ultimately it becomes a priority species. Colonies are invariably small and scattered, which may pose problems for recolonisation. Noar Hill in Hampshire has always been an excellent site.
The Brown Argus (Plebeius agestis, wingspan 29mm) is a member of the blue family but carries none of that colour, which helps in identifying it compared with other blues coloured principally brown, notably the female Common Blue (Polyommatus icarus, wingspan 35mm). It is also smaller. The main foodplant is Common Rock-rose (Helianthemum nummularium), which means the Brown Argus is very much at home on chalk and limestone grassland. The species enjoyed a significant increase in numbers during the 1990s which appears to have halted.
The Common Blue lives up to its name, being found almost anywhere that the foodplant Birsdfoot Trefoil grows. The male has no brown colouring but the female can be mainly brown or a marvellous mixture, as in the image above. There are usually two broods, in June and August-September, and sometimes a third.
The Small Heath (Coenonympha pamphilus, wingspan 35mm) breeds in virtually any location where Fescues and Bents (wild, fine-leaved grasses) flourish. Properly managed downland offers excellent opportunities for this active little creature, which, together with the Silver-spotted Skipper, can be very tough to approach closely.
Marbled Whites (Melanargia galathea, wingspan 48mm) also require grasses for their caterpillars and are found in various habitats but downland, where they can be prolific in July, seems to suit them best. In fact they have been doing better than most species of butterfly over the last 20 years, expanding their range north and east from the southern stronghold.
Small Coppers (Lycaenas phlaeas, wingspan 32mm) are at home wherever their usual foodplants, Common Sorrel (Rumex acetosa) and Sheep's Sorrel (Rumex acetosella), grow. This can include heathland, woodland clearings and coastal dunes as well as downland, and it is hardly surprising the species is common. Equally, its numbers declined in the 20th century.
There can be three broods a year from May to October, and some carry blue spots on the wings. These are less common in southern Britain than in Scotland, particularly the far north of that country.
Clouded Yellows (Colias croceus, wingspan 55mm) are annual visitors in varying numbers to the whole of Britain, migrating from the Mediterranean. They cannot survive cold conditions but with the increasing mildness of our winters they may well end up being able to overwinter in southern England.
They already have one brood, hatching in August from arrivals in May and feeding on clover, lucerne and trefoil, and in a good year they can present one of the outstanding sights when arriving in bulk on the coast, and on the downs in particular after successful breeding.
Another species which, with warmer conditions, stands every chance of colonising is the Queen of Spain Fritillary (Argynnis lathonia, wingspan 42mm), an attractive continental species which has been making occasional forays to southern Britain for centuries, sometimes leading to small broods being reared in August of the year they arrive.
There was a short-lived breeding colony in Suffolk in the late 1990s (the caterpillars feed on Field Pansy, Viola arvensis), and with the number of visitors increasing as the species has grown in scale in Normandy in the 21st century there is a chance of long-term colonisation occurring. A number were seen in Sussex in 2009 and mating definitely occurred.
Images © Jeremy Early. All rights reserved.
In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.