The Alder Leaf Beetle in Nottinghamshire
 
Once regarded as being extinct in the UK and even considered as being a migratory species, the Alder Leaf Beetle Agelastica alni (Linnaeus, 1758) has recently undergone a sudden expansion of range, with a string of records stretching from Merseyside, across the country to the Humber.
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Scattered records from many southern counties of the UK, would perhaps tend to agree with Agelastica alni having migratory tendencies.

But after being found in Nottinghamshire for the first time in 2014, it looks as though this dark, metallic blue leaf beetle, has colonised the county from populations in the north-west UK.

Hundreds were recorded on the banks of the River Don in Sheffield City centre and from Chesterfield (Dutton, C.) either side of Nottinghamshire's first record at Dyscarr Wood, north of Worksop (Bradford, P.) on June 11th.

Present UK status

A nationally rare beetle which was previously believed to be extinct in the UK. However, there have been numerous recent records, so its current status of is unknown and has RDB K (insufficiently known) status.

 
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On the basis of the recent increase in records and UK range, it will almost certainly be downgraded to a lesser status at a future date.

Nottinghamshire records and current distribution

To date (September 2015) Agelastica alni has been recorded from five Nottinghamshire sites. All but one of these (Dyscarr Wood) are former Colliery sites and all are in the north-west of the county around Mansfield and Worksop. Nottinghamshire's first record was from Dyscarr Wood, when it was found and photographed by Pauline Bradford on June 11th 2014. We later recorded it from Warsop Main Pit Top on September 20th 2014.

In early 2015, records again came from the known sites of Dyscarr Wood and Warsop Main Pit Top, but we soon started to receive records from other sites. In April 2015, it was found on Shirebrook Pit Wood by Cliff Toplis, then recorded from Langold by Rob Johnson and Jane Carruthers and later at Shireoaks Pit Top by Rob Johnson.

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Above right: Agelastica alni habitat at Warsop Main Pit Top in September 2014. A total of 20 adults were found, mostly on the small Alder growing right of centre in the photograph. The lower photograph of the two, shows a small section of Alder growing at Manton Pit Wood, Worksop, infested with adult beetles in September 2015.

Preferred habitat and some observational notes

Five of the six known sites for Agelastica alni in Nottinghamshire, are the former Colliery spoil heaps of Shirebrook, Warsop Main, Manton, Shireoaks and Firbeck Collieries. All are found in the north-west of the county. The other currently known site (as of September 2015) of Dyscarr Wood, is actually a Nottinghamshire Wildife Trust reserve. There are presently no records from former Colliery sites south of Mansfield and east of Worksop, but that looks likely to change in the next few years.

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  Sites so far producing negative results for Agelastica alni include Bevercotes Pit Wood, Ollerton Pit Wood, Brierley Forest Park and Gedling Country Park.

Several years after closure, the spoil heaps of all of Nottinghamshire's former Collieries were topped with a stone aggregate and soil, then planted with a mix of both deciduous and coniferous trees. The range of deciduous trees included Alder (Alnus glutinosa) and other species of Alnus.

Small trees and young regenerative growth are generally most favoured by Agelastica alni, but these soon become stripped of foliage in cases of large numbers of both adults and larvae. As seen at Manton Pit Wood in September 2015, replacement leaf growth is attacked later in the Summer/Autumn, with adults moving to other Alders as food supply becomes short.

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Above: Agelastica alni damage to regenerative Alder growth at Manton Pit Wood in September 2015. The Alder in the foreground was untouched.

Whilst Alder is clearly the preferred foodpant, we recorded numerous adults feeding on isolated examples of Birch (Betula pendula) and Goat Sallow (Salix caprea) at Manton Pit Wood. Adult Agelastica alni can be found from April to July and then again in September, with adults occasionally remaining active into early October.

     
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