|Obrium brunneum (Fabricius, 1793)|
|Quoted as extremely rare and doubtfully indigenous by
Hickin, this species is not included in either Fowler or Joy.
According to Alexander it is an accidental introduction
occuring south of the Thames. Twinn and Harding include
thirteen records, mostly near coastal, from east Dorset to south Kent and of these six are from before 1970, a similar
spread of records is presented on the NBN map (2009). We are therefore surprised to have recorded a specimen swept from
mature oak (Quercus robor) in Whippendell wood during June 2009. The species is associated with conifers and
recorded hosts include Abies excelsa, Pinus, Picea and Larix; at the location of our record there are a few
large and healthly larch and many pines ranging from healthy to insect ridden and a few dead including several large
fallen specimens. Larvae feed beneath the bark of recently felled or dead boles and branches, when fully mature they bore
into the outer xylem and excavate an elongate pupal cell, the adults emerge from May and occur until July. The life cycle
takes a year. Adults have been recorded visiting flowers of Apiaceae (various umbels), Spiraea and Viburnum
(Bily and Mehl)
Small; 4-7mm (Bily and Mehl) and entirely testaceous or dark testaceous with fine pale yellow pubescence which is erect on the head and pronotum and backwardly recumbent on the elytra. Head shiny, finely and sparsely punctured, obliquely included forward in front of antennal insertions. Across eyes a little wider than pronotum. Temples weakly contracted behind eyes then subparallel to base. Eyes strongly emarginate and curved around antennal insertions. Antennae slender, only slightly overlapping elytral apices, segment 2 shorter than others, 1-4 with scattered setae, 5-11 with dense short pubescence. Pronotum elongate, without lateral borders or teeth but with a large rounded tubercle at middle, upper surface with three indistinct raised areas; one either side of middle and one medially in front of base. Finely punctured, as head but more densely so, puncturation much stronger in front of basal margin. Front and hind margin about equal in width, both finely margined. Front coxal cavities closed behind, obvious and easily appreciated in side view; technically diagnostic but in any case the species distinctive. Elytra dilated behind middle and evenly rounded apically, completely covering abdomen, humeri well developed. Puncturation fine and sparse, becoming obsolete behind middle. Wings full; the specimen featured was observed in flight. Legs long and slender; femora strongly clavate. Tibiae long; hind tibiae extending beyond elytra in natural setting, each with two small spurs on inside at apex. Front tibiae smooth, without grooves. Claws relatively large, smooth and without internal appendages.
Description from one Watford specimen at X20
A second species of Obrium Dejean, O.cantharinum (L., 1767) is included on our latest checklist (Rejzek in Duff, 2008). Twinn and Harding (1999) include only six pre-1970 records and conclude that the species is now extinct. Uhthoff-Kaufmann (1985) reviewed its occurence in Britain and noted pre-1850 records from Herts and Essex and twentieth century records from Kent, the most recent (reliable) record is from Devon in 1929 (Perkins, 1929). Hyman and parsons (Ibid) and Shirt (1987) also list the species as distinct.
Both species are key by Bily and Mehl (Ibid) and Duffy and the differences are straightforward:
1. Pronotum smooth and shiny. Elytra light; orange testaceous. Scutellum subparallel. 5-9mm..........cantharinum (L.)
- Pronotum dull and finely punctured. Elytra dark brown. Scutellum triangular or nearly so. 4-7mm....brunneum (Fab.)
Perkins, R.C.L. 1929 Obrium cantharinum in Devon. Ent.Mon.Mag. 65:261
Shirt, D.B. 1987 British red data book: 2, Insects Nature conservancy council.
Uhthoff-Kaufmann,R.R. 1985 The genus Obrium in Great Britain; a reappraisal. Ent.Rec.J.Var 97:216-223.