An exceptional influx …
The summer of 2026 is proving to be one of the most remarkable recent seasons for sightings of the Queen of Spain Fritillary Issoria lathonia (Lepidoptera: Nymphalidae) in Britain. Normally a scarce migrant, the species has appeared in Norfolk and at numerous sites in southern England, including Kent, Sussex, Surrey, Hampshire, and the Isle of Wight, with several locations holding multiple individuals. The scale and distribution of the records raise the intriguing possibility that some butterflies may represent locally-emerging individuals, although continued immigration from continental Europe is also likely.
Issoria lathonia is widespread across North Africa and much of continental Europe, including breeding populations in northern France, Belgium and the Netherlands. Britain therefore lies relatively close to established populations, and favourable conditions can facilitate immigration across the Channel.
The present run of records became particularly conspicuous in late June. A Queen of Spain Fritillary recorded at Stoke Bottom in West Sussex on 28th June was unusually early for the county, where August and September are more typical months for the species. Further records subsequently appeared at sites across southern England, including the Isle of Wight and Hampshire.
This is where the 2026 influx becomes particularly interesting. Issoria lathonia is multivoltine and can develop rapidly in warm conditions, and the appearance of butterflies later in the season can, in some circumstances, indicate a new generation produced after an earlier immigration event. Such an interpretation cannot be applied to every 2026 record, however, because continued immigration from continental Europe is also likely.
Numbers have been particularly impressive at some southern sites. On the Isle of Wight, at least two individuals were recorded together in late July, while at Monk Sherborne in Hampshire, several individuals were present and subsequent reports continued into late August. Local observers have suggested that the Monk Sherborne concentration may have involved around 10-15 butterflies, although that figure should be regarded as an estimate rather than a confirmed count.
The species' habitat requirements are not obviously restrictive. It favours warm, open habitats where Wild Pansy Viola tricolor and Field Pansy V. arvensis occur. Both foodplants are widespread in southern Britain, providing extensive potential breeding habitat. The greater challenge may be overwintering successfully. The species is generally considered unable to survive traditional British winters reliably, although temporary breeding populations have occurred. In 2009, for example, an immigrant female in West Sussex was followed by a later generation, and the event was regarded as a possible attempt to establish a colony.
There have been several notable episodes of immigration and temporary breeding in Britain, including 2007, 2009, 2017 and 2022. The latter produced an especially striking concentration in Kent, where 46 records were submitted, many involving multiple individuals. None of these episodes has so far resulted in a persistent mainland population.
It is therefore too early to describe Issoria lathonia as established in Britain. What can be said with confidence is that 2026 has produced an unusually large and widespread occurrence by modern standards. The distribution and timing of the records are consistent with continued immigration, while the presence of multiple individuals at some sites raises the possibility that breeding has also occurred. The coming months will be especially significant. If butterflies produced during 2026 can overwinter successfully and reproduce again in 2027, this remarkable season could prove an important step in the species' continuing north-westward expansion.
References:
Eeles, P. (2023). British & Irish Butterfly Rarities - Migrants, Extinctions & Introductions. Newbury, Berkshire: Pisces Publications, pp. 132-143.
https://www.birdguides.com/news/record-queen-of-spain-fritillary-influx-to-england/?utm_campaign=7460888_Weekly%20News%20from%20BirdGuides%2024%2F08%2F2026&utm_medium=email&utm_source=dotdigital&dm_i=73DM,4FWUW,ZVAF9,BQLDS,1,0,0,0 [Accessed, 24th August 2026].
https://www.ukbutterflies.co.uk/phpBB/viewtopic.php?t=12561 [Accessed, 24th August 2026].
https://www.ukbutterflies.co.uk/species.php?species=lathonia [Accessed, 24th August 2026].