Agelastica alni
In 3 days ~50% in a week ~80%
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 |
Possible
About 20% of wildlife watchers report an Alder Leaf Beetle sighting in Helsinki on a given day, based on 257 verified sightings from GBIF citizen-science data. It is the 6th most-seen of the 838 insects we can rate there. Over three days the chance rises to about 50%, and over a week to about 80%, if each day is a fresh chance.
May–June and August
In those months about 30% of wildlife watchers report an Alder Leaf Beetle in Helsinki on a given day, against under 5% in December to 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.
3rd of 23
Of the 23 cities where we can rate Alder Leaf Beetle sightings, Helsinki ranks 3rd at about 20%. The best odds are in Liverpool (United Kingdom, about 40%) and Manchester (United Kingdom, about 40%).
Same family: Chrysomelidae
The closest relatives of the Alder Leaf Beetle that you can see in Helsinki (family Chrysomelidae, Leaf Beetles) are Western Grape Rootworm (about 10%), Chrysolina sanguinolenta (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 Helsinki (257 verified sightings), 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.
