The Large Poplar Longhorn Beetle Saperda carcharias in the Scottish Highlands

The Biodiversity and Management of Aspen woodlands: Proceedings of a one-day conference held in Kingussie, Scotland, on 25th May 2001

Tracey Begg
Department of Zoology, University of Glasgow. Email: tracey.begg@rspb.org.uk

Iain MacGowan
Scottish Natural Heritage, Battleby, Redgorton, Perth. Email: Iain.MacGowan@snh.gov.uk

Large Poplar longhorn beetle, Saperda carcharias © Lorne Gill/SNH By being an agent in the thinning process, Saperda carcharias acts in an ecologically beneficial manner and plays an important role in the ecology of Aspen stands.

The Large Poplar longhorn beetle Saperda carcharias (Linnaeus) (Cerambycidae), is classified as a notable A species considered to occur in 30 or fewer 10km Grid Squares of the National Grid (Hyman and Parsons, 1992). In the Scottish Highlands, the known distribution of this species has recently been extended from four to 13 10km squares (MacGowan and Begg In Prep.).

Larvae of Saperda carcharias are found in trunks of Aspen (Populus tremula) the preferred larval tree, but other Poplar species, Salix and occasionally Quercus may be utilised (Uhthoff-Kaufmann, 1991).

Saperda probably spends 2-4 years as a larva within an aspen tree (Hyman and Parson, 1992), after which the adults emerge during July and August. Adults may be found until October. During the emergence period, frass and wood fibres are ejected through a circular hole in the bark formed by an enlargement of the oviposition site. This makes it possible to determine where larvae are present and adults have emerged.

Studies conducted at two sites, Invertromie in Strathspey and a site in Deeside during the emergence period in 2000, revealed that where trees had emergence holes, or showed signs of larval activity, the tree circumference (measured at chest height) was within the range 13-187cm. The mean circumference was 47.4cm.

The circumference of over 200 Aspen trees across the Scottish Highlands was measured and showed that the mean circumference for aspen overall lies in the 81-90cm circumference size range. This demonstrates that Saperda carcharias is selecting for smaller trees.

Within each aspen stand, most activity was found to be on trees at the edge of the stand, next to open ground with only a few sites being found within dense cover. Trees found bordering walls, fences or along road verges commonly had an abundance of emergence holes, possibly due to the open aspect consistent with these sites.

Where conditions are favourable and grazing pressure is low, Aspen regenerates by producing suckers from the parent tree, giving rise to dense stands of young trees. These trees are used by Saperda larvae. Although larval activity does not directly kill the host tree, it no doubt weakens it by allowing the entry of damaging tree diseases, fungal attack and by weakening the stem, making it more susceptible to wind blow and other damage.

The thinning of Aspen stands to produce relatively open stands of larger trees is, in general, a benefit to the other insects and lichens associated with Aspen. By being an agent in the thinning process, Saperda carcharias acts in an ecologically beneficial manner and plays an important role in the ecology of Aspen stands.

References

Hyman and Parsons. 1992. A review of the scarce and threatened Coleoptera of Great Britain, Part 1, UK Nature Conservation Series Number 3, Joint Nature Conservancy Council, Peterborough.

MacGowan, I. and Begg, T. 2001. Notes on the distribution, status and ecology of the large poplar long-horn beetle, Saperda carcharias (Linnaeus) (Cerambycidae) in the Scottish Highlands. In Prep.

Uhthoff-Kaufmann, R. R. 1991. The distribution and occurrence of the genus Saperda F. (Col. Lamiidae) in Great Britain. Entomologists Record 103: 129-134.

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For further information about aspen, please go to the Aspen Information Resource

Pages about beetles on this site

• Beetle Survey in Glen Affric 2004
• Beetle Survey in Glen Affric 2005
• Beetles occurring in Glen Affric
• Beetle Survey on Dundreggan in 2007-08
• Beetles occurring on the Dundreggan estate
• The Large Poplar Longhorn Beetle Saperda carcharias in the Scottish Highlands
• Byctiscus populi, a leaf rolling weevil dependent on Aspen