Agelastica alni

{{short description|Species of beetle}}

{{Speciesbox

| image = Agelastica alni.jpg

| genus = Agelastica

| display_parents = 4

| species = alni

| authority = (Linnaeus, 1758)

| synonyms =

; sensu stricto:

• Adimonia violacea Laicharting, 1781
• Cryptocephalus violacea Geoffroy, 1762
• Chrysomela alni Linnaeus, 1758

; glabra:

• Adimonia glabra Fischer von Waldheim, 1842
• Agelastica sillemi Laboissière, 1935
• Agelastica orientalis Baly, 1878

| synonyms_ref = {{cite book|last=Beenen|first=R.|year=2010|chapter=Galerucinae Latreille, 1802|url=https://books.google.com/books?id=qt8zDwAAQBAJ&pg=PA455|pages=443–491|editor1-last=Löbl|editor1-first=I.|editor2-last=Smetana|editor2-first=A.|title=Catalogue of Palaearctic Coleoptera. Volume 6. Chrysomeloidea|publisher=Apollo Books|place=Stenstrup, Denmark|isbn=978-87-88757-84-2}}{{cite journal|last=Bezděk|first=J.|year=2015|title=A review of palaearctic Scelolyperus (Coleoptera: Chrysomelidae: Galerucinae), with description of S. perreus sp. nov. from Turkey|url=https://www.researchgate.net/publication/274633922|journal=Annales Zoologici|volume=65|issue=1|pages=21–39|doi=10.3161/00034541ANZ2015.65.1.003}}

| range_map = Agelastica alni distribution map.png

}}

Agelastica alni, the alder leaf beetle, is a species of leaf beetle (Chrysomelidae) in the genus Agelastica.{{cite web|url=https://www.biolib.cz/en/taxon/id11907/ |title=Agelastica alni |website=BioLib.cz |date= |accessdate=2017-03-31}} Agelastica alni is distributed in Europe, the Caucasus, Siberia, north-eastern Kazakhstan, and in the 19th century was introduced to the United States.{{cite book |last1=Kolk |first1=A |last2=Starzyk |first2=J.R. |title=Atlas szkodliwych owadów leśnych (The atlas of harmful forest insects) |date=1996 |publisher=The Polish Forest Research Institute. Multico Ofic. Wyd. |location=Warszawa |pages=705}}

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{{cite web |url=https://www.rhs.org.uk/advice/profile?PID=850 |title=Alder leaf beetle |accessdate=11 June 2019 |last=RHS |first= |date=2019 |work= |publisher=Royal Horticultural Society}} 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,{{cite web|url=http://www.probertencyclopaedia.com:80/cgi-bin/res.pl?keyword=Alder+Leaf+Beetle&offset=0 |archive-url=https://web.archive.org/web/20091219073802/http://www.probertencyclopaedia.com/cgi-bin/res.pl?keyword=Alder+Leaf+Beetle&offset=0 |url-status=dead |archive-date=2009-12-19 |title=Alder Leaf Beetle |accessdate=2017-03-31 }} 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.{{Cite web|url=http://www.deeside.com/a-beetle-thought-to-have-been-extinct-in-britain-has-been-found-in-northop/|title=A beetle thought to have been extinct in Britain has been found in ..... Northop Deeside.com|website=www.deeside.com|access-date=2018-08-16}} This beetle has now been seen in North Yorkshire as of 29-09-24.