Agelastica alni
In 3 days ~30% in a week ~60%
Agelastica alni, the alder leaf beetle, is a species of leaf beetle (Chrysomelidae) in the genus Agelastica. Agelastica alni is distributed in Europe, the Caucasus, Siberia, north-eastern Kazakhstan, and in the 19th century was introduced to the United States.
The beetle and the beetle's larval host is the grey or speckled alder (Alnus incana) and to a lesser extent black alder (Alnus glutinosa), but it will also be found on hazel, birch or hornbeam if there is a shortage of food. It causes large holes and gaps in leaves from the end of April onwards, which are produced by the larvae in the first two stages, but the main damage is produced by larvae in the third stage.
Previously rare, and considered extinct in the UK, since being found in Manchester in 2004 it appears to be on the increase in the North West of England. Its range has been extending and it was found in Nottinghamshire and Hampshire in 2014 and in North Wales in 2018. This beetle has now been seen in North Yorkshire as of 29-09-24. Seen in York as of 15.5.25
The alder leaf beetle is a relatively small beetle, around 6–7 mm, black or metallic blue in colour. The winged adults overwinter and emerge in... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Biebrza National Park | 🇵🇱 Poland | |
| 2 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 3 | Białowieża National Park | 🇵🇱 Poland | |
| 4 | Wadden Sea National Park | 🇩🇪 Germany | |
| 5 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 6 | Cévennes National Park | 🇫🇷 France |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Liverpool | 🇬🇧 United Kingdom | |
| 2 | Manchester | 🇬🇧 United Kingdom | |
| 3 | Helsinki | 🇫🇮 Finland | |
| 4 | Leeds | 🇬🇧 United Kingdom | |
| 5 | Essen | 🇩🇪 Germany | |
| 6 | Birmingham | 🇬🇧 United Kingdom | |
| 7 | Bishkek | 🇰🇬 Kyrgyzstan | |
| 8 | Rotterdam [The Hague] | 🇳🇱 Netherlands | |
| 9 | London | 🇬🇧 United Kingdom | |
| 10 | Hamburg | 🇩🇪 Germany |
With luck
About 10% of wildlife watchers report an Alder Leaf Beetle sighting in Snowdonia National Park on a given day, based on 20 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 117th most-seen of the 387 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 60%, if each day is a fresh chance.
May–June and November
In those months about 20% of wildlife watchers report an Alder Leaf Beetle in Snowdonia National Park on a given day, against under 5% in August and December–March, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Alder Leaf Beetle sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
2nd of 6
Of the 6 parks where we can rate Alder Leaf Beetle sightings, Snowdonia National Park ranks 2nd at about 10%. The best odds are in Biebrza National Park (Poland, about 20%).
Same family: Chrysomelidae
The closest relatives of the Alder Leaf Beetle that you can see in Snowdonia National Park (family Chrysomelidae, Leaf Beetles) are Bloody-Nosed Beetle (about 20%), Green Dock Beetle (about 10%) and Poplar Leaf Beetle (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Alder Leaf Beetle is recorded against all the insects logged in Snowdonia National Park (20 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
