Month: September 2025

Hedgerows are dripping with fruit, blackberries resplendent in bunches like grapes, nuts browning on Hazel, haws crimson in autumn sunlight, Dog-rose fruits glowing orange, wild Crab-apples larger than ever, all showing the results of a balanced summer: well-watered, warm and sunny.

I mention fruit because butterflies are resorting to hedgerows, enjoying the sugary juices.  Remaining flowers, mostly Dandelion, Ivy, and Devil’s-bit Scabious, also continue to attract remaining butterflies.

But with cooling temperatures, longer nights and diminishing resources, what butterflies can we hope to see in October?

Few species can be found in abundance except in certain coastal areas where pre-migratory Red Admirals gather for a final feed before departure. Look for them on Ivy and in orchards, where fallen fruit or fruit opened by wasp jaws leaks their sweetness. Elsewhere, Red Admiral will be found in low numbers, but it remains a presence in suitable hedgerows during October.

The Comma is another late emerger. It is probably our latest emerging butterfly now. They continue to fly throughout October, feeding on blackberries and Ivy before finding a sleeping place deep in woodland, deep hedges and scrub where they remain until next March. The autumn Comma is much deeper in colour than the direct-breeding summer generation. The colour differences are striking, but some paler Comma hatch in autumn, but these are rarely as golden as their summer predecessors.

This year, the Small Copper produced an autumn generation, a third brood. These are mostly feeding on Dandelions but also on blackberries. These are breeding, not hibernating or migrating. After mating, females feed for several days before beginning their task of locating suitable sorrels to lay their eggs. The caterpillars that result will feed until entering a hibernation state. Feeding by the caterpillars is resumed in spring when daylight increases and the sorrel shows fresh growth. The adult Small Coppers next spring are likely the offspring of two generations, of the second and third brood of 2025, for not all second-generation adults likely produced eggs that resulted in adult butterflies in 2025.

The Speckled Wood is still on the wing in October. These might be second-generation Speckled Woods or third-generation. This butterfly has an unusual brood structure, which makes the brood provenance of adults impossible to identify. A unique feature is its ability to pass the winter in the larval and pupal state. All the other Irish species pass the winter in a single life stage. 

This year, excellent weather during August allowed over-wintering species that emerge in that month to complete their pre-winter feeding, so sightings of Brimstone, Small Tortoiseshell and Peacock will be few.

The occasional migrating Clouded Yellow will be seen. This is most often seen in October in Ireland, except in years when it arrives earlier and in abundance. Enjoy October.

All images © J. Harding

The Painted Lady Vanessa cardui is an attractive migrant butterfly. It appears in Britain and Ireland every year. It is less numerous than the Red Admiral but more numerous than the Clouded Yellow, our other regular migrant butterflies. It is closely related to the Red Admiral and similar in size, with wingspans ranging from about 58mm to 74mm, with males smaller than females. Sexes look alike. Its uppersides are dark brown, orange and white with small, faint blue markings on the anal angle of the hindwings. The hindwing underside is mottled buff, white and slate blue, while the forewing pattern imitates the forewing upperside, but the broad band is pink, not orange. In fresh butterflies, the uppersides can show a lovely pink flush. The Painted Lady is seen in Ireland mainly during the summer and early autumn.

The butterfly is our most mobile species and can appear anywhere there are nectar sources, especially if thistles, the food for the larvae, are present. The butterfly breeds in Ireland during the summer, but the caterpillar cannot survive temperatures below five degrees Celsius. The Painted Lady has no ‘rest phase’ in its life cycle, and when conditions no longer favour breeding, the butterfly must migrate to find suitable conditions.

In the past, the view was that the Painted Lady migrated to Britain, Ireland and northern Europe, but that all life stages of the butterfly died when cold weather arrived. This view was supported by the almost complete absence of observed southward migration from northerly areas in autumn. However, research carried out since 2008 provides fascinating information about the butterfly’s migration.

Where do Painted Lady butterflies migrate to? How do we know where migrating Painted Lady butterflies originate?

The Painted Lady performs an annual multi-generational migration between Europe and North Africa. Its seasonal appearance south of the Sahara in autumn is well known and has led to the suggestion that it results from extremely long migratory flights by European butterflies to seasonally exploit the Sahel and the tropical savannah. However, this possibility had not been proven. However, a study by Constanti Stefanescu and his colleagues that analysed the isotopic composition of Painted Lady butterflies from seven European and seven African countries provides support for this hypothesis. Each butterfly was assigned a geographical natal (birth) origin, based on its wing stable hydrogen isotope (d2 Hw) value and a predicted d2 Hw basemap for Europe and northern Africa.

Isotopes are two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element. Isotopes of hydrogen are different across Europe and Africa, with regional variations in their abundance due to differences in climate, rainfall patterns, and moisture sources. While the three main hydrogen isotopes (protium ¹H), deuterium (²H), and tritium (³H)) are naturally occurring, their stable isotopic ratios (expressed as δ²H) vary geographically, with more depleted values found in temperate and boreal regions of Europe and higher values closer to the tropics and coastal areas in Africa. These differences in hydrological hydrogen are reliable across Europe, North Africa and sub-Saharan Africa, enabling researchers to identify the origin of migrating Painted Lady butterflies.

Natal assignments of autumn migrants collected south of the Sahara (Sahel) confirmed long-distance movements (of 4,000 km or more) starting in Europe. Samples from Maghreb (north-west Africa) revealed a mixed origin of migrants, with most individuals having a European origin, but others having originated in the Sahel. Therefore, autumn movements are not only directed to northwestern Africa but also include southward and northward flights across the Sahara. Through this remarkable behaviour, the productive but highly seasonal region south of the Sahara (the area receives rain in June and July) is incorporated into the migratory circuit of the Painted Lady.

How do we know about high altitude migration, and how do Painted Lady butterflies travel such long distances?

Migration of the Painted Lady to north-eastern Spain is aided by African wind currents that show a strong correlation between wind patterns and the ability of the butterfly to migrate long distances in a corresponding direction, concluding that the butterfly rides on the wind currents in the upper levels of the atmosphere when undertaking long-distance flights. This was confirmed by Jason Chapman and Rebecca Nesbit using vertical-looking radar to show that the insects regularly fly at a height of up to 1,200 m. In the reverse (southbound) autumn migration in 2009, most flew at between 200 and 400  Chapman and Nesbit wrote: “Wind speeds 500m above the ground are often four or five times faster than the butterflies’ flight speed, so that if they are able to fly at these heights they could reach speeds of almost 100km/hr (60 mph)”. High altitude flights are prevalent southwards from Europe in autumn.

I observed how these high-altitude flights are launched by the Painted Lady and the Red Admiral. Individual butterflies typically use level flight when moving through the landscape, but in autumn, while migratory flight at eye level occurs, high altitude flight is mostly used. Individual butterflies fly upward in a vertical or near-vertical trajectory, eventually disappearing from the view of the observer on the ground. When a following wind is located, likely, level flight at altitude is then adopted to help the butterfly move toward its destination.

Journeys northwards into Europe in spring and summer are made by successive generations of Painted Lady butterflies. Stefanescu and his colleagues state: “The migratory cycle in this species involves six generations, encompassing a latitudinal shift of thousands of kilometres”. This is a round-trip extending from Africa to above the Arctic Circle of over 13,000 kilometres.

However, as stated earlier, we also know that individual Painted Lady butterflies fly as many as 4,000 km when migrating from Europe to sub-Saharan Africa in autumn.

Another method that has been used to track butterfly movement is telemetry, when radio tags are fixed to a butterfly. A tag fitted to a Swallowtail butterfly’s head was used to track its movements in the Maltese Islands over an approximate period of two weeks of field monitoring. The release site was Comino, the island between Malta and the second-largest Maltese Island, Gozo. Tagged Swallowtail Papilio machaon melitensis individuals were recorded to undertake a short sea crossing between the islands of Comino and Gozo, subsequently, each making their way to the northern side of Gozo. Each butterfly is estimated to have covered a minimum distance of approximately 16.6 km in 17 days.

While the Swallowtail (wingspan up to 93mm) is larger than the Painted Lady, it is conceivable that the Painted Lady might be tracked using telemetry in the future. (The Swallowtail is dispersive within Malta, but elsewhere it will migrate. The migration rate of Papilio machaon in North America was estimated at 4.3 km per day in upwind conditions (Sperling and Harrison, 1994). In favourable weather conditions (downwind), this rate is probably higher.

What triggers the Painted Lady’s migration?

The research has concluded that the reason for migration is the need to locate and exploit abundant but temporary resources over large geographical areas. But what are the cues that drive the species to migrate? For now, these remain unknown.

The theory is that northward migration in spring is triggered by population density, increasing daylight hours, increasing temperatures, increasing aridity and decreasing nectar and larval host plant resources. Southward migration from Europe might be triggered by the decreasing light levels, falling temperatures, and diminishing nectar and host plant resources.

The wonder of Painted Lady migration

Whatever the causes, the migration of the Painted Lady is a fascinating chapter in the story of our butterflies. Adding to this wonderment is the sheer scale of these mass movements. While some migrations occur over weeks and span wide geographical areas, others are concentrated over a shorter period of time and within narrower spatial zones. I saw hundreds of Painted Ladies in Kinvara, County Galway, on May 30, 2009, flying off the Atlantic to settle on Red Valerian, trees, shrubs and even the coast road where they were crushed by traffic. I travelled home that afternoon, watching the butterflies fly across roads during my eastward journey through Galway. It is estimated that 11 million Painted Lady butterflies arrived in these islands in May 2009, but that 21 million left Britain and Ireland that autumn. Many accounts of thousands of caterpillars were recorded. An estimated 500,000 Painted Lady caterpillars were recorded in two fallow fields near Port Isaac, Cornwall.

Another mass migration occurred in 2019, when millions arrived. One County Down gardener reported 100 or more in his coastal garden, on lavender, on August 1. Hundreds of adults were recorded on Tory Island, Co. Donegal, on the previous day. 

An unusual aspect of the 2019 mass migration was that it followed two years of large migrations. Typically, the year or years following a mass Painted Lady migration see very low numbers in Ireland. In 2010, following the millions that arrived in 2009, the Painted Lady was very scarce in Ireland. I saw one Painted Lady in 2010, a famine following a feast. Another unusual feature of the 2019 migration is that it began on January 10, when at least 20 were seen near Bere Island on the south side of Fair Head, County Cork.  However, the main arrivals occurred in June, July and August. High numbers were recorded during September 2019, but by mid-September, the figures declined as reverse migration occurred. Few were seen in Ireland during 2020.

Such spectacular migrations are impressive, but in California, one migration was estimated to contain three billion Painted Lady butterflies! Given its rapid development rate (the egg to adult stage I observed in 2019 lasted 54 days, but this will be shorter in warmer conditions),  impressive migratory capability and the wide range of larval food plants it uses, it is understandable that it is probably the most successful butterfly on Earth, occurring on all continents except South America.

When you admire a Painted Lady in your garden in late summer or autumn, keep this thought in mind: in a few days, it could be flitting between blooms on the African savannah south of the Sahara, in the company of African Lions, Leopards and Dama Gazelles.

Key References

Chapman, J. W. and Nesbit, R. L. (2008). Mysteries of Lepidoptera migration revealed by entomological radar. Atropos. 35, pp. 28-36.

Grech, N. (2021). Investigating ecological corridors and barriers to movement: a species approach for conservation (Master’s dissertation). University of Malta https://www.um.edu.mt/library/oar/handle/123456789/94093

Sperling, F.A.H.; Harrison, R.G. (1994). Mitochondrial DNA variation within and between species of the Papilio machaon group of swallowtail butterflies. Evolution  48, 408–422.

Stefanescu C, Soto DX, Talavera G, Vila R, Hobson KA. (2016). Long-distance autumn migration across the Sahara by painted lady butterflies: exploiting resource pulses in the tropical savannah. Biol. Lett. 12: 20160561. http://dx.doi.org/10.1098/rsbl.2016.0561

Stefanescu, Constantí; Páramo, Ferran; Åkesson, Susanne; Alarcón, Marta; Ávila, Anna; Brereton, Tom; Carnicer, Jofre; Cassar, Louis F.; Fox, Richard; Heliölä, Janne; Hill, Jane K.; Hirneisen, Norbert; Kjellén, Nils; Kühn, Elisabeth; Kuussaari, Mikko; Leskinen, Matti; Liechti, Felix; Musche, Martin; Regan, Eugenie C.; Reynolds, Don R.; Roy, David B.; Ryrholm, Nils; Schmaljohann, Heiko; Settele, Josef; Thomas, Chris D.; van Swaay, Chris; Chapman, Jason W., Multi-generational long-distance migration of insects: studying the painted lady butterfly in the Western Palaearctic Ecography (Copenhagen), 2013-04 Vol.36 (4), p.474-486

All photographs copyright J. Harding.

 

 

Ivy Hedera helix is an evergreen climber found in hedges, on trees, walls and on the ground, in shaded places. The plant flowers mainly during August, September and October. The value of Ivy for pollinators lies in its abundance in the landscape and the timing of its flowering. By early September, most grassland herbs have finished flowering. Warm, sheltered, lightly managed hedges containing Ivy in flower are ideal places for pollinators, and these are well worth checking in sunny weather during autumn. Ivy hosts nocturnal insects, too. Moths like Herald and Red-green Carpet take nectar during darkness, while hoverflies, bees, wasps, flies and butterflies visit during the day.

Here are some species that use flowering Ivy.

A tip for nature lovers in September and October is to check the flowering Ivy in coastal areas. Red Admiral and Painted Lady will gorge on Ivy before flying seaward. Hundreds have been observed on Ivy on the south Wexford coast (Slade) in autumn.  It provides food and roost sites for pre-migration butterflies. 

Ivy is also used by overwintering insects. The Brimstone is adapted to use Ivy. Its wing shape imitates Ivy leaves, even including blotch marks on the underside of the wings.

Comma may use it too.  The Comma underside has a leaf-like appearance, mimicking a dead oak leaf. Dense Ivy will hold dead leaves from other plants. Being evergreen, it conceals and shelters.

Ivy is also used as a larval foodplant by the Holly Blue. Its caterpillar relies on Ivy berries in late summer and autumn. Double-striped Pug, Yellow-barred Brindle, Willow Beauty,  Dot Moth, Old Lady and Small Angle Shades are macro-moths that use Ivy as their larval foodplant, among other plants. 

Allowing Ivy to flower is crucial if you want to help autumn insects. If it must be trimmed, do this in February, after the worst of the winter weather is over, but avoid trimming all your Ivy in any year. Variety helps biodiversity.

 

 

 

 

‘Season of mists and mellow fruitfulness,’ enthused Keats about autumn, but this year has witnessed an abrupt change as a dry, sunny August ended. Keats’ autumn was sunny, gentle and bountiful, but September 2025 has been wet so far, so butterflies are less visible, but appear quite abundant when the sun shines. This post looks at some of the butterflies we can expect to observe this month. 

The Green-veined White, Large White and Small White are confusion species. We show images of all three and describe some key differences.

The Green-veined White can be separated by habitat preference. It rarely appears in cultural habitats such as urban parks and urban and suburban gardens, due to its avoidance of dry habitats. It prefers moist, humid habitats, including moist hedgerow margins, vegetated ditches, ponds with watercress, wet grassland, fens, marshes, damp rides in woodland, bog margins, and wilder rural gardens.

The Large and Small Whites prefer drier places. These are happy in green spaces in towns and cities, especially gardens containing brassicas, allotments, brownfield sites, ‘Linnet plots’ on farmland, dry coastal habitats and generally anywhere with flowers and brassicas, but neither breeds in the damp places favoured by the Green-veined White.

All three can be found together in some places containing moist and dry conditions, such as coastal areas containing dune slacks (moist) and eroding dunes (dry), fields with damp and dry areas, and rural gardens and other places with flowers where all three will occur to take nectar. Another identification challenge is that the Large White and Small White are highly mobile and can appear anywhere, but neither breeds in humid places. 

All images 2025 copyright Jesmond Harding