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Chris van Swaay @chrisvanswaay.bsky.social · 2d

Now the 2025 field season for butterflies has come to an end, it is a good moment to look back at the great work of the recorders of Dutch Butterfly Monitoring transects. Almost 400,000 butterflies counted in 2025 on 1372 locations, 8,5 million since 1990 on 212,327 km. Thanks for all hard work!

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Chris van Swaay @chrisvanswaay.bsky.social · 7d

2025 will mark another bad year for the Dark Green Frit (grote parelmoer, S aglaja) with numbers comparable to 2023 and 2024 in NL (=low). Once widespread throughout the country, and numbers ten years ago still good, now reasonable numbers only on Vlieland and N-Texel (the islands in the NW).

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Chris van Swaay @chrisvanswaay.bsky.social · 8d

2025 marks a very bad year for the Glanville Frit (veldparelmoer, M cinxia) in NL. Only the coastal population had >10 butterflies, on the inland ones the species almost vanished. Poor weather in 2024 made few larvae enter last winter.

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Chris van Swaay @chrisvanswaay.bsky.social · 9d

The Painted Lady (distelvlinder, V cardui) was only seen in low numbers on Dutch Butterfly Monitoring transects this year. It is a migrant species, and the graphs show that 1996, 2003, 2009 and 2019 had large invasions, the other years just a few managed their way to NL.

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Reposted by Chris van Swaay

Trouw @trouw.nl · 12d

Veel meer natuur nodig om nuttige insecten voor de landbouw te behouden

Regels van de EU die tot herstel van de insectenpopulatie moeten leiden zijn ontoereikend, blijkt uit Wagenings onderzoek dat donderdag gepubliceerd is in het wetenschappelijke tijdschrift Science.

www.trouw.nl

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Chris van Swaay @chrisvanswaay.bsky.social · 12d

www.trouw.nl/duurzaamheid...

Veel meer natuur nodig om nuttige insecten voor de landbouw te behouden

Regels van de EU die tot herstel van de insectenpopulatie moeten leiden zijn ontoereikend, blijkt uit Wagenings onderzoek dat donderdag gepubliceerd is in het wetenschappelijke tijdschrift Science.

www.trouw.nl

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Chris van Swaay @chrisvanswaay.bsky.social · 22d

The Swallowtail (koninginnenpage, P machaon) had a good year on Dutch Butterfly Monitoring transects, clearly better than 2024 (though we have had better years). Exceptional was the large 3rd generation, which is usually small in NL.

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Chris van Swaay @chrisvanswaay.bsky.social · 28d

The addition of flexcounts, as eg 15min counts, to Dutch Butterfly Monitoring transects, makes it possible to produce detailed flight curves. Although 2025 was warmer, the White Admiral (kleine ijsvogel, L camilla) had an earlier start in 2024. Also watch the small 2nd gen.

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 8

An interesting pattern for the abundance of the Common Blue (icarusblauwtje, P icarus) on Dutch Butterfly Monitoring transects: a large and early 1st gen, followed by a smaller 2nd gen (which is normally larger than the 1st gen) and a small 3rd gen right now. Food quality in summer has been poor.

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Reposted by Chris van Swaay

Mr and Mrs Trellis @thenorfolkcoast.bsky.social · Sep 7

Semi-natural grasslands as a nature-based solution for climate change mitigation: An assessment of carbon and plant communities across age gradients...

www.sciencedirect.com/science/arti...

Semi-natural grasslands as a nature-based solution for climate change mitigation: An assessment of carbon and plant communities across age gradients

Semi-natural grasslands have the potential to sequester carbon and enhance biodiversity and therefore offer opportunities as nature-based solutions fo…

www.sciencedirect.com

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 4

Though I wonder, because it is normally typical for C hyale to be attrackted to its host plant, C alfacariensis feeds on H comosa and Coronilla varia and probably others). They can only be seperated by DNA or by larvae (which are relatively easy to id).

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 4

It is clearly a Colias hyale/alfacariensis, which cannot be separated in the field, but C hyale does not occur (as far as I know) south of the Alps, so this must be alfacariensis.

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 4

The Hummingbird hawk-moth (kolibrievlinder, Macroglossum stellatarum) is a climate opportunist from the south, and they love warm weather. Numbers on Dutch Butterfly Monitoring transects were high this summer, and the next generation just started. So watch out for these 'hummingbirds' in your garden

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 3

Colias alfacariensis

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 2

This is a Clouded Yellow Colias croceus, another species, and a migrant from the south.

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 2

It's been a while since we had a good migration year for the Pale Clouded Yellow (gele luzernevlinder, C hyale) on Dutch Butterfly Monitoring transects, but finally numbers are comparable to 1992, 2003, 2006 and 2017. The species declined in C Europe, the origin of our butterflies.

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 1

No, we don’t monitor hibernators, would be interesting.

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Chris van Swaay @chrisvanswaay.bsky.social · Sep 1

After a great start this spring the Peacock (dagpauwoog, A io) had a poor 1st gen in July, and the 2nd gen is more or less absent on Dutch Butterfly Monitoring transects. Numbers are now much lower than in 2024.

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 31

Enjoy!

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 31

Yesterday I bumped into this fresh male Sooty Copper (bruine vuurvlinder, L tityrus), of what will probably become a 3rd gen. Also a new site for me on S Veluwe. This species shows a large decline, esp. in the north of NL, since I started butterflying.

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 26

Pity not as 15min count. Would still be in the north, comparable to Denmark, so would fit in the general picture.

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 26

Not that long ago in August Buddleia's could be covered with Small Tortoiseshells (A urticae, kleine vos). On eBMS transects and 15min counts (www.butterfly-monitoring.net) this butterfly is now restricted to higher elevations or latitudes. Open squares=counted in that period.

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 25

An update of the Pieris-whites on Dutch Butterfly Monitoring transects show they all have a relatively poor 3rd gen this year. The reason recorders feel they 'only count Whites' is because all other species are doing even worse, maybe except for C hyale and C argiades in the SE.

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 24

But remember P rapae also puts eggs on the same plant. Check your young larvae, they are different in the first two stages, with P mannii having a black head and P rapae a green head. See lepiforum.org/wiki/page/Pi... and lepiforum.org/wiki/page/Pi.... Older larvae cannot be separated.

Pieris mannii - LepiWiki

lepiforum.org

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Chris van Swaay @chrisvanswaay.bsky.social · Aug 24

Clouded and Pale Clouded Yellow (C hyale+crocea, gele en oranje luzernevlinder) are migrants in NL and show large year-year fluctuations in density on Dutch Butterfly Monitoring transects. Before 1980 C hyale was considered more abundant, now it is C croceus. Numbers for 2025 up to now.

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