Northern Ireland's Priority Species

Dorcatoma dresdensis – a beetle

 

Dorcatoma dresdensis Herbst, 1792
Family: Anobiidae

Dorcatoma dresdensis belongs to the woodworm beetle family Anobiidae which is poorly represented in Ireland and has only twenty-one species compared to fifty-three in Britain. Anobiids are mainly associated with old growth forest and feed on dead, infected and/or decaying wood, some members specialising on other types of plant food such as stored biscuits, tobacco etc.
In appearance anobiids can be very disparate. The subfamily Xyletininae to which Dorcatoma belongs are all small insects (1.5-4 mm) with broad, not very elongate, elytra, broad pronotum and head with pectinate (having narrow parallel projections or divisions suggestive of the teeth of a comb) antennae. Dorcatoma has slightly elongate elytra while other genera are quadrate (equal in length and width). The present species was recorded for the first time in Ireland in 2009 (Alexander, 2009). It was reared from fruiting bodies of the oak bracket Inonotus dryadeus collected on Inisherk Island, Crom, Upper Lough Erne.

In brief

  • This is a N. Ireland Priority species and recorded for the first time in Ireland in 2009
  • Widespread but rare in the southern UK, and a notable species (Na)
  • Found feeding on Inonotus dryadeus, the oak bracket, in Crom Estate, Co. Fermanagh

Species description
The subfamily Xyletininae to which Dorcatoma belongs are all small insects (1.5-4 mm) with broad, not very elongate, elytra, broad pronotum and head with pectinate antennae. Dorcatoma has slightly elongate elytra while other genera are quadrate (equal in length and width). Dorcatoma dresdensis is dark with red legs and antennae and differs from other Dorcatoma in a combination of large eyes, shining upper surface with equal-sized punctures and recumbent pubescence parallel or nearly parallel to the suture. It is 2-2.6 mm long.

Life cycle
The larva feeds on decaying bracket fungi on trees. In Britain Ganoderma austral, which is common on beech in Ireland, and Phellinus pomaceus which is widespread but uncommon on blackthorn, have been used. In Britain Inonotus dryadeus is host to a related species Dorcatoma serra Panzer, which has not so far been recorded from Ireland.

Similar species
See Species Description

How to see this species
Alexander (2009) sampled bracket fungi from Caledon Park, Baronscourt Deer Park and Castle Ward Park which had exit holes suggesting the presence of Dorcatoma, but unfortunately without finding live adults. Large brackets on oak with exit holes from these and other sites, can be stored in moist rearing chambers to see whether adult Dorcatoma emerge. This can take some time, up to a year or so. The chances of seeing this species in the field are probably remote.

Current status
The species is recorded with certainty only from Crom Castle Estate, Co. Fermanagh. Nevertheless, it could occur more widely and is possibly under-recorded. It is not known to be under threat but the removal of veteran oaks would obviously be inimical to its survival.

Why is this species a priority in Northern Ireland?

  • This species has only one recorded site and is therefore vulnerable
  • It has Northern Ireland Priority status and is Na in the UK
  • The family Anobiidae to which it belongs is saproxylic (associated with old growth forests) and very under-recorded in Ireland

Threats/Causes of decline
Removal of veteran trees, particularly oak.

Conservation of this species

Current action
Declaration as a Priority Species.

Proposed objectives/actions

  • A re-examination is required, of sites where exit holes in large bracket fungi were noted by Alexander

What you can do
This is a rare and elusive species about which more information is required. It should be looked for in bracket fungi growing on ancient oaks. If you encounter something which suggests this species please note the locality from an OS map and report the details, with a specimen or specimens to CEDaR (Record Centre Manager, CEDaR, National Museums Northern Ireland, Cultra, Holywood, Co. Down, BT18 0EU; cedar.info@nmni.com).

Further information

Links

Literature
Alexander, K.N.A. (2009). Dorcatoma dresdensis Herbst (Coleoptera: Anobiidae): a beetle new to the Irish list. Irish Naturalists' Journal 30: 66.
Harde, K.W. (1984). A field guide in colour to beetles. Octopus Books, Czechoslovakia. [very good - sometimes obtainable secondhand on Ebay].
Johnson, W.F. & Halbert, J.N. (1902). A list of the beetles of Ireland. Proceedings of the Royal Irish Academy 6(3): 741.
Joy, N.H. (1932). A practical handbook of British beetles. Witherby & Sons, London.

Text written by:
Dr Roy Anderson