Hylurgops palliatus (Gyllenhal, 1813)
Quoted simply as local by Joy and Duffy, Fowler outlines a wide national distribution and writes 'local, but common where it occurs... appears to be the most common species of Hylastes (=Hylurgops) in some parts of southern England. Scotland, common in the bark of fir logs'. Locally the species occurs throughout Whippendell wood and adjacent woodlands and when found it is usually in numbers. During 2009 adults were common under the bark of fallen pine trunks and logs during April and May, and then again in August (no searching was done during June or July); at this time along with abundant larvae in galleries excavated underneath loose bark; sometimes the galleries and surrounding area are covered by a thick layer of black wood dust and frass and so are not immediately obvious although in such cases an outline of the galleries is visible on the outer xylem. In most cases the beetles were present along with the scolytid Dryocoetes autographus (Ratz.), and sometimes Dryocoetes was much more abundant. The larvae observed during August, always along with abundant adults of both beetles, varied in size and probably represented more than one instar. The association of these two species is well known and pointed out by Bevan. Some aspects of the species biology (from Poland) are outlined by Kolk and Starzyk, from which the following notes are taken. Hylurgops infests both fallen and standing timber, generally damaged or dying parts and usually the lower parts of trunks where the bark is thick. The species is said to prefer shaded conditions and this is often the case in Whippendell wood although fallen trunks in open situations exposed to the sun were also found to host the species. With the exception of yew (Taxus) all conifer species may host the species (Duffy quotes Abies, Pinus, Picea and Larix). Larvae or pupae overwinter in galleries while adults spend the winter under bark or among forest litter. Adults become active in April or May and again in July and August and there are two generations each year. Females excavate galleries 4-6mm long and around 1.5mm wide, usually a single gallery with a hook-like bend at the top. Larval galleries are long and run almost parallel from the maternal gallery. Pupation occurs in the sapwood (=lower surface of bark, beneath the cambium) and young adults commence 'maturation feeding' in galleries so that in large populations the pattern of galleries becomes confused. Female Dryocoetes sometimes lay eggs in the current egg galleries of Hylurgops which may explain the association we see locally, and the abundant larvae we see may thus represent both species.

2.3-3.5mm. Elongate cylindrical and parallel sided, brown to black with head generally darker. Head visible from above, produced into a short and broad rostrum in front of eyes; puncturation coarse and close, confluent in some areas, surface between punctures somewhat shiny, pubescence fine and short. Pubescence on rostrum long and pointing forward. Eyes transverse and entire. Antennae inserted on side of rostrum at base; scape curved and dilated towards apex, funiculus 7 segmented; basal segment large and quadrate, remainder becoming more transverse towards apex, club broadly oval and pointed. Pronotum slightly transverse (8:9), without borders or sculpture, punctures wide and close, even but for a smooth line along centre, at least in basal half. Widest just before middle, basal half parallel, narrowed anteriorly and appearing sinuate behind front angles. Elytra parallel sided with a steep apical declivity, basal margins separately rounded exposing a small scutellum, nor, or only weakly raised and without tubercles (c.f. Tomicus). Striae strongly punctured, these striae may touch, especially towards apex. Interstices strongly microsculptured, in places transversely rugose, and weakly tuberculate towards apex, each with a single row of pale, semi-erect setae, these may become confused towards base. Legs robust, concolorous with body. Tibiae gradually widened to apices, outer margin toothed from base to apex. Protibiae longitudinally excavate from middle to apex to receive tarsi and with a curved, outwardly facing tooth inside at apex. Third tarsal segemnt bilobed. Claws small, smooth and without a basal tooth.

Description from 6 Watford specimens at X40