Trypodendron domesticum (Linnaeus, 1758)
This species is generally common throughout Europe and Asia Minor from the Mediterranean north to Scandinavia and the UK and also in northwest Africa, it was first recorded from North America in 2008 and is now established in some northern states as well as in Canada. In the UK it occurs in established woodland and parkland with old deciduous trees throughout England and Wales and more sporadically further north to the Scottish Highlands. Adults occur year-round; they overwinter in short subcortical galleries and emerge in early spring to commence feeding before mating occurs, swarming and dispersal occurs in March or April and continues until May and there may be another dispersal flight during June. Females bore short, 5-7 cm, but deep oviposition galleries through the sapwood of wide variety of broadleaf trees and gnaw small notches at regular intervals in which they deposit an egg, larvae develop through the summer, producing short and broad galleries about 5mm in length which are soon producing mycelia upon which they feed, perpendicular to the oviposition gallery, pupation occurs at the end of the larval gallery and adults emerge from mid-summer. There are thought to be two generations, or a sister generation, each year in Europe and this may be the case also in southern parts of the UK. Historically this has been a very destructive species of commercially grown hard woods in Europe and there are still occasional large outbreaks in northern areas; although bark beetles are usually attracted to ethanol produced by fermenting sap, especially on damaged areas of bark or on drought-stressed trees, this species is also known to attack healthy trees and is suspected to be a major contributory factor in the recent decline of beech trees across Belgium.
Adults are generally distinctive due to the elytral colouration but two other Trypodendron species occur in the UK and are superficially similar; domesticum is distinguished by the form of the antennal club which is rounded to an almost perpendicular inner angle, in our other species it is more rounded and not sharply angled internally. A small, 3.0-3.8mm and parallel-sided species with the head hidden beneath the pronotum in dorsal view; head distinctive, eyes completely divided and antennae pale with a 4-segmented funiculus and a large single segmented club. Entire dorsal surface finely pubescent but this is longer and most obvious beyond the elytral declivity. Pronotum entirely black or diffusely red near the posterior angles, slightly transverse and a little wider than the base of the elytra, rounded anteriorly and almost parallel behind the middle, posterior angles rounded and basal margin finely bordered although this may be obscured by sculpture; surface with arcuate transverse series of broad tubercles which continue into the middle of the base, along the base laterally smooth and medially with rather dense blunt round tubercles. In lateral view evenly rounded dorsally and almost perpendicular anteriorly, front margin steeply declined to a rounded ventral margin. Elytra pale brown with the suture and lateral margins variously black, striae punctured and distinct near the suture, otherwise variable and usually depressed on the declivity, interstices flat over the basal two-thirds, convex towards the apex, declivity distinctly angled. Legs long and robust, all tibiae curved and finely toothed externally, tarsi without bilobed segments.
Trypodendron domesticum 1
Trypodendron domesticum 2
Trypodendron domesticum 3