Hornet moth (Sesia apiformis) in Wageningen floodplains (NL). We see them every year, but still fun. Hoornaarvlinder (Sesia apiformis) in Wageningse uiterwaarden. We zien ze elk jaar, maar het blijft leuk.

As May progresses we slowly sink into a few weeks with low numbers of butterflies in NL. We used to call this the June-dip, but more and more of it occurs in May as a result of climate warming. Spring butterflies are almost gone, and summer butterflies start emerging around mid June.

Although the Holly Blue (boomblauwtje, C argiolus) is often seen in gardens, on Dutch Butterfly Monitoring transects by far the highest density is counted on heathland, where Common Heather (Calluna vulgaris) is an important foodplant.

This year sees an early arrival of Painted Ladies (distevlinder, V cardui) on Dutch Butterfly Monitoring transects. These butterflies come from the Mediterranean and migrated north through France. In some years the can be very abundant (eg 2009 and 2019), in other years almost missing.

A very poor spring generation of the Map (Landkaartje, A levana) on Dutch Butterfly Monitoring transects. Numbers are much lower than in 2025, but also lower than in most of 1990-2025. Low quality nettles because of the dry spring of 2025 caused a poor 3rd gen and low numbers now.

A relatively good year for the Orange Tip (oranjetipje, A cardamines) on Dutch Butterfly Monitoring transects. Last week we crossed the peak level and numers are going down again. The graphs also shows we have to start the season before 1 April or we miss part of the flight period.

Rake Loesje!

Where the distribution (=occupancy) of the Large white (groot koolwitje, P brassicae) is stable, it occurs everywhere, the population level is now significantly lower on Dutch Butterfly Monitoring transects, in spite of strong fluctuations. After 2008 the pop index never was >100.

Low numbers of Peacock (dagpauwoog, A io) on Dutch Butterfly Monitoring transects this year, after last years poor summer generation and missing 2nd gen because of poor quality nettles. This spring is also dry and much too warm so far, so things don't look good for nettles and peacocks this year.

Numbers of Chequered Skipper (bont dikkopje, C palaemon) can fluctuate a lot, but the last few years have been bad for the species with a decline of 70% since 1990. Also distribution (=occupancy) declined with 30%. As a species of moist woodland it has a problem with dry summers.

Density of Brimstone (citroenvlinder, G rhamni) on Dutch Butterfly Monitoring transects this spring higher than in spring 2025, but also higher than in summer 2025 (and these are the same butterflies as they hibernate as adult). They probably hibernated (or aestivated) quickly after emerging.

The increase of the Orangetip (oranjetipje, A cardamines) on Dutch Butterfly Monitoring transects (=populatie) is partly due to the expansion of the species (=occupancy) by 30%, but also the density has gone up between 1990 and 2025. If you go out now, you have a good chance of seeing this butterfly

The last 20 years the 2nd generation of the Dingy Skipper (Bruin dikkopje, E tages) in NL has become larger and larger, with the peak of the first generation moving weeks forward.

The mean flight date of the Orangetip (A cardamines) is now more than two weeks earlier than in 1990 on Dutch Butterfly Monitoring transects, though there are large fluctuations from year to year, depending on spring weather.

This is craziness on a mega scale. A 5C increase in spring temperatures in the arctic alpine zone in just c 30 years. The result is that forest is spreading north at 1km a year. It’s driving several endemic butterflies extinct. www.bc-europe.eu/webpage.php?...

Met de Samenhangende aanpak Landbouw, Natuur en Stikstof kiest ook de nieuwe Minister van Natuur voor mest, ammoniak, vervuiling en verder natuurverlies. Er zijn twee structurele tekortkomingen bij dit voorstel. open.overheid.nl/documenten/6...

Did you know we also record butterfly–flower interactions? 🦋🌸 Three decades of observations show how species loss limits the capacity of communities to reorganize their interactions in response to environmental change. 📄Read the scientific article: l1nq.com/L5wls

Addressing Gaps in Butterfly Population Monitoring to Catalyze Global Insect Conservation. This paper calculates a “Global Butterfly Index” using the Living Planet Index approach, paving the way for a global network of butterfly monitoring schemes. conbio.onlinelibrary.wiley.com/doi/10.1111/...

Trends of 2e gen Wall (argusvlinder, L megera) on Dutch Butterfly Monitoring transects show 3 groups: more or less stable in coastal dunes, 80-90% decline on semi-natural grassland and urban and 95-99% decline in agriculture and woodland.

Very different populationtrends for the Gatekeeper (oranje zandoogje, P tithonus) on Dutch Butterfly Monitoring transects: increase in the coastal dunes, declines in NE, more or less stable in the rest. And we don't really know why.

Butterfly density (numbers per 1000m) on Dutch Butterfly Monitoring transects in 2025 if each transect would have been counted each week. Only transects between 500-3000m length are used. Highest densities on islands in SW and along the IJssel river, lowest in low polders in Holland and Friesland.

Prof Paul Ehrlich has died at 93 I interviewed him in 2018, 50 years after the publication of The Population Bomb “Too many rich people in the world is a major threat to the human future, and cultural and genetic diversity are great human resources.” www.theguardian.com/cities/2018/...

New research in #RESInsectConsDiv Contribution of #CitizenSciences to the production of #butterfly species long-term trends doi.org/10.1111/icad.70066 #Biodiversity #MonitoringSchemes @manusaunders.bsky.social @wileyecology.bsky.social

Smoothed trend 1992-2025 of most Dutch butterflies from Dutch Butterfly Monitoring transects. The color indicates the linear trend over the whole period. Each line starts at a value of 100. The black dot gives the 2025 index value.

After the extremly hot and dry summer of 2018 numbers of the Dark green fritillary (S aglaja, grote parelmoer) on Dutch Butterfly Monitoring transects crashed and has not recovered. I fear it could get extinct in NL soon, what is amazing for a species that can live in so many different habitats.

Here is the full paper #conservationevidence @richardfoxbc.bsky.social @djhbutterflies.bsky.social @martinswarren.bsky.social @ukbutterflies.bsky.social @savebutterflies.bsky.social @chrisvanswaay.bsky.social @pietervantieghem.bsky.social besjournals.onlinelibrary.wiley.com/doi/10.1002/...

The density of the Common Blue (P icarus) per 50km square in 2024 on eBMS Butterfly monitoring transects (www.butterfly-monitoring.net) shows a W-E cline, with lowest densities in Ireland, UK, Portugal and NL and highest in Sweden, Austria, Italy and Balkans.

In 2025 the number of transects where expert volunteers count butterflies in NL rose to almost 1600. On most of them (1257) all butterflies are counted, but some transects are for one species only or plots for egg-counts.

Begin januari gaf de Rechtbank Noord-Nederland aan dat gegevens over het gebruik van pesticiden beschikbaar moeten worden gesteld aan belanghebbenden. Om deze vereiste transparantie te traineren gaat de staatsecretaris nu in hoger beroep. uitspraken.rechtspraak.nl/details?id=E...

Number of butterfly species per 5x5km square in Netherlands in 2025. The richest sites are on the Veluwe (centre) and South Limburg (southeast). The open polders in N Holland, Friesland, Groningen and Flevoland have the least number of species.

2025 was another bad year for the Chequered Skipper in NL. The distribution of this butterfly is getting more and more sparse. The species cannot cope very well with the dry years since 2018.

Our second Masterclass in identifying European butterflies is coming up next Wednesday 17th Feb. This one covers the trickier species in the Atlantic region given by renowned expert Chris van Swaay. The Webinar zoom link: us06web.zoom.us/j/81934375118

Pearly heath & Alpine heath form a complex of seemingly integrades in the southern Alps known under the name Darwin's heath - Coenonympha (gardetta) darwiniana. Here's the 4 players in that complex, check ALT text for more info on these species in the making #darwinday #dailylepi #butterflies

For all who more or less know the butterflies of NW Europe, but find the diversity of the Balkans overwhelming, there is a masterclass on "Eastern continental and Balkan butterfly species" by Rudi Verovnik on 11th February at 15h CET. For more details see butterfly-monitoring.net/epic-butterfly

The Small Heath (hooibeestje, C pamphilus) experienced a huge crash in 1991 on Dutch Butterfly Monitoring transects, maybe caused by extreme cold nights (-8C) in April. Though numbers are slowly going up, the species never fully recovered. #vlindermaand

Brown Hairstreak (sleedoornpage, Thecla betulae) is a local species in NL, and can be found in the centre of the country where sandy soils meet clay, often in urban areas, as well as in S Limburg (SE NL). This distribution has been more or less unchanged for the last 30 years. #vlindermaand

The Green-veined White (klein geaderd witje, P napi) is still widespread and common in NL, but numbers have halved since 1990 on Dutch Butterfly Monitoring transects. With the species preferring moist circumstances, the increasing number of droughts by climatechange surely have effect. #vlindermaand

The Sooty Copper (L tityrus, bruine vuurvlinder) has shown serious declines, esp. in the north of NL. Only on the Veluwe (centre) the situation is better. This species is vulnerable to N deposition (fartmann.net/downloads/ar...).

The Gatekeeper (P tithonus, oranje zandoogje) is doing well in de coastal dune-transects of the Dutch Butterfly Monitoring Scheme, but shows declines in the Agricultural area (where most transects are in verges) and esp. woodland. We don't know why the trend on woodland is so negative. #vlindermaand

Large and Small tortoiseshell (grote en kleine vos, N polychloros and A urticae) show opposite trends in their distribution in NL. The Large T used to be rare, and is now widespread, esp. in the eastern half. The Small T is now rare outside the W and N. #vlindermaand

As NL is at the NW-edge of the distribution of the Swallowtail (koninginnenpage, P machaon) we see periods of expansion (2009-2013 and 2018-2025) alternate with periods of retraction (2014-2017). #vlindermaand

Camouflage: Green Hairstreak - Groentje - Callophryx rubi. #vlindermaand

Around 1990 the Queen of Spain Fritillary (I lathonia, kleine parelmoer) in NL was restricted to the coastal dunes. After 2000 the inland was colonised, but not from the coast, but from the southeast (B and D). In 2024 the species crashed, some recovery in 2025. #vlindermaand

www.trouw.nl/duurzaamheid... Mooi interview met @dickvanhoffen.bsky.social. Onderbouwd tegewicht tegen de mantra ‘Alles moet dood’ uit de BBB-gelederen…

Even though the Meadow Brown (M jurtina, bruin zandoogje) is the most abundant butterfly on Dutch Butterfly Monitoring transects, it is missing or rare in some parts of the country. #vlindermaand

In the 1990s the Comma (P c-album, gehakkelde aurelia) would have a large extra Sept generation. However this Sept generation became smaller and smaller and nowadays only a few butterflies are present in Sept and most of the summer butterflies go straight into hibernation. #vlindermaand