|Lymexylidae Timberworm Beetles|
The only family included within the Lymexylidae, includes the two British species in two subfamilies:
Hylecoetus dermestoides (L.) within the Hylecoetinae and Lymexylon navale (L.) classified within the
Lymexylinae. Hurka gives the species
Elateroides dermestoides (L.) and states that 'until recently this species has been classified in the genus
Hylecotoides Latreille'. There is no mention of Elateroides in our latest check list (Booth, R.G. in
Duff). Lohse (1979) gives two species of Hylecoetus; dermestoides
(L.) and flabellicornis Schneider as well as Lymexylon navale and there is no mention of
Elateroides presumably Elateroides is our Hylecoetus.
These are medium sized, 7-18mm, elongate and cylindrical beetles with soft, brown or yellowish and densely and very finely punctate and pubescent elytra which do not fully cover the abdomen. The abdominal apex (which is soft and so easily distorted) tapers to a point. In both species the elytra narrow towards the apex and so become divergent. Antennae black with basal segments yellow, 11 segmented and inserted on the side of the head in front of the eyes. Eyes large and protruding. In the males the maxillary palpi are greatly enlarged and tuft-like. Legs yellow and relatively long. Tarsi 5-5-5, segments elongate and without lobes (a character which will separate them from similarly coloured cantharids where the abdomen is sometimes exposed beyond the elytral apex).
Our two species are readily separated:
1. Pronotum transverse, distinctly and diffusely punctured. Scutellum with a raised triangular carina. Antennae short; weakly serrate in female, more strongly so in male. Male with head and pronotum black, elytra yellow with apex black. Female entirely yellow......Hylecoetus Latreille
- Pronotum quadrate, very finely punctured. Scutellum with a raised carina. Antennae long; filiform in male, very weakly serrate in female. Male with head black, pronotum black with anterior part and hind angles yellow, to almost entirely black, elytra black with base gradually, or sometimes obscurely, orange. Female with head black, pronotum orange, elytra orange at base darkening to pitchy at apex.......Lymexylon Fabricius
Both species are associated with woodland or wooded pasture (etc) where the larvae develop within a range of trees. The larvae are unique with the first thoracic segment enlarged into a hood like process, this being proportionally much longer in Hylecoetus. The terminal segment is also modified; in Hylecoetus this is large and reflexed forming a long, upright horn-like process with lateral and terminal setae. In Lymexylon this segment is produced into a large oblique lobe. Both characters, thoracic and terminal, are obvious in the pupa. The first instar larva is different; strongly sclerotized and flat with a large head, thid stage bores into the bark, later instars live in galleries which they bore into the wood.
Both species are local; Joy gives England and northeast Scotland for Hylecoetus and England south to Lincs for Lymexylon. The NBN maps (April 2009) a mainly southeastern distribution for Lymexylon while Hylecoetus occurs mostly above a line from the Severn to the Wash with single records from the west country (north Devon) and the Scottish Highlands. The impression is that the two are allopatric. Our few Watford records do not reflect this.
Freude,H.,Hurde,K.W.Lohse,G.A. 1979 Die Kafer Mitteleuropas Vol 6 pp100-101 Glocke and Evers