‘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 upperside of the female Green-veined White shows the veins picked out in a dusting of dark scales. The female Large White and Small White also show two spots on the forewing upperside, but no vein markings. In the Green-veined White, the black apical patch extends further down the costa (leading edge) than along the termen (outer edge).The male Green-veined White has a single spot on its forewing upperside. The markings along the veins are weaker than in the female.Green-veined White (underside) on Devil’s-bit Scabious. This butterfly has been remarkably abundant in the summer and continues to fly in high numbers in early September. The vein markings are more prominent on the underside in this species, in both sexes.Large White female. The apical patch on the forewing extends an equal distance along the costa (leading edge) and termen (outer edge), unlike in the Small White. The Large White is notably larger (wingspan typically 58-62mm, sometimes larger) than the Green-veined White (45mm-50mm) and Small White (38-56mm), which often appear to be the same size. The Large White enjoyed abundance throughout July and August, which has continued into September.Unlike the male Green-veined White and Small White, the Large White male has no spot on its uppersides. It shows a single spot on its forewing underside.Large White underside. Note the large square black spot on the forewing underside. The female Large White has two underside spots on the forewing; the male has one.The female Small White has two spots on its forewing uppersides, like the female Large White and Green-veined White. Note the lemon wash; most are milky white on their uppersides. The apical patch extends further down the costa (outer edge) than along the termen (outer edge). The Small White was common this summer, but it probably did not match the other two common whites in abundance. A Small White male. Like the male Green-veined White, it has a single spot on the forewing upperside. The black apical patch extends further down the costa (outer edge) than along the termen (outer edge). Small White underside. This example has a richly coloured hindwing and apical patch on the forewing; many are paler. Some Large Whites are similar in colour but are notably larger.
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.
Clouded Yellow. Watch out for this beautiful migrant. It has been recorded in recent weeks.Red Admiral remains abundant in September, but many are departing for warmer regions. Look for it on garden flowers and wild blooms.Is the Comma on blackberries the most evocative image of autumn?This female Comma was sunning itself in a south-facing hedge. Commas often bask in hedges and trees.The Small Tortoiseshell feeds on flowers in gardens, fields, and anywhere there are flowers, but usually close to a hibernation site. During late summer and early autumn, they often enter buildings to seek a dark corner in which to pass the coldest months.The Speckled Wood is one of the most abundant species in September. It likes feeding on apples that have been attacked by wasps.Flower-rich, nutrient-poor grasslands are the places to look for Devil’s-bit Scabious, which flowers profusely during September. These flowers serve a nectar banquet to autumn pollinators.Devil’s-bit Scabious also host the larval nests of the Marsh Fritillary butterfly. September is a great month to search for the nests.Butterflies continue to breed during September; here are Large White eggs on Nasturtium. There is still a lot to see!
