Hylis Gozis, 1886

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POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

EUCNEMIDAE Eschscholtz, 1829

MELASINAE Fleming, 1821

EPIPHANINI Muona, 1993

H. cariniceps (Reitter, 1902)

H. olexai (Palm, 1955)

-3-5mm. Head with a finely raised median keel which may be faint or confused among the punctures in places (view from in front). Pronotum moderately densely punctured, the punctures separated by about their own diameter, central impression weakly developed or almost absent. Scutellum trapezoidal and rounded. Third metatarsomere at least twice as long as wide. Male with a transverse furrow behind the clypeus.

Hylis olexai

-4.6.5mm. Head with a more strongly raised and well-defined median keel. Pronotum densely punctured, the punctures on the disc almost touching in places, central longitudinal impression deep and well-defined to the middle. Scutellum triangular and rounded apically. Third metatarsomere about 1.5X longer than wide. Male without a transverse furrow behind the clypeus. Compared with females the males have longer antennae, segments 7-11 distinctly and regularly longer in comparison.

Hylis cariniceps

Hylis cariniceps (Reitter, 1902)

Although widespread across Europe from Spain to Yugoslavia and Greece and north to the UK and the south of Fennoscandia, this species occurs sporadically and is generally scarce and very local throughout its range. In the UK it has only recently been discovered and is known from a very few sites in South Hampshire and Somerset, it is a species of old established woodland and so considered to be native and overlooked rather than introduced. Adults usually occur in open woodland with plenty of dead wood and fallen timber, they have been recorded from a range of trees on the continent, mostly broadleaf and often on aspen (Populus tremula L.), but also (rarely) from conifers, they occur from late spring until September and are active by day as well as at night. Larvae develop among moist decaying wood in fallen trunks and branches that contact the soil and have been reared from a range of species including hornbeam (Carpinus betulus L.), hazel (Corylus avellana L.), aspen, hawthorn (Crataegus spp.)  and Norway spruce (Picea abies L.), and also from ivy (Hedera helix L.).

Superficially similar to the below species but more strongly sculptured and so appearing duller, it is generally larger and darker in colour but they overlap, distinguishing characters are mostly subtle but the following key will separate the species.

Hylis olexai 1

Hylis olexai 1

Hylis cariniceps 1

Hylis cariniceps 1

© Lech Borowiec http://www.cassidae.uni.wroc.pl/Colpolon/index.htm

Hylis olexai 2

Hylis olexai 2

Hylis olexai 3

Hylis olexai 3

Hylis olexai (Palm, 1955)

Originally introduced to the UK list as Hypocoelus procerulus Olexa, 1954 in 1954, this species remained very rare over the following decades but seems to have increased in range and abundance in recent years, it is now locally common in the southeast below a line from The Wash to Hampshire and there are a few scattered records from The West Country. In Europe it is among the commonest members of the genus, it is widespread in central Europe extending north to southern Fennoscandia and south to Italy, Croatia and Bulgaria,  it is absent from many Mediterranean regions and rare and very local in some northern regions e.g. there is only a single record from Poland. Typical habitats are open woodland and parkland with plenty of dead and fallen timber and it may be more frequent in such habitats in chalk and limestone districts, it is associated with a range of trees including pine, spruce, poplar and chestnut but probably most often with beech. Adults occur over a short season from April or May until August and will usually be found in large numbers, by day they hide under bark or among cracks and layers of dry xylem although in warm sunny weather they also run on the surface of dry fallen wood and they may be observed mating early in the season, but they are crepuscular and nocturnal as well and are easily seen on the surface by torchlight. They generally occur on fallen trees or branches and on log stacks, in South Herts. we have recorded them from stacked hornbeam logs and in South Hants among stacked pine trunks, and at another South Herts. site they are very common on a large fallen beech tree. Larvae develop under an intact outer layer of soft wood or among damp heartwood in hollows etc, but little is known of the life-cycle, adults have not been recorded earlier than April and so pupation occurs early or late in the year. Adults are easily sampled by pootering although they can run fast and vanish into crevices when alarmed, they can also jump like an elaterid but much more weakly so and they only rarely do.

In general form very suggestive of an elaterid but readily distinguished by the eccentric placement of the second antennomere on the first. 3-5mm. Elongate-oval, broadest across the base of the pronotum with the elytra almost parallel-sided in the basal half, body entirely dark brown to almost black, entire dorsal surface with pale recumbent pubescence, appendages paler brown. Head transverse with large and convex eyes, vertex and frons with a fine but distinct longitudinal ridge, otherwise evenly convex and densely punctured. Antennae inserted anteriorly , the insertions separated by about the length of the basal segment, long and very gradually thickened towards the apex, basal segment with an external  lateral tooth in front of the middle and behind the (lateral) insertion of the second segment, second segment shorter than the second and basal segment, 3-5 elongate, 6 and 7 quadrate or nearly so, 8-10 elongate and rounded internally in the male, slightly transverse in the female, terminal segment long and pointed. Pronotum evenly curved laterally from a rounded anterior margin to posteriorly-produced and sharp hind angles, basal margin strongly bisinuate, surface densely and moderately strongly punctured, the punctures separated by about their diameter, and with a weakly developed longitudinal impression towards the base, otherwise evenly convex. Elytral shoulders rounded, lateral margin sub-parallel in the basal half then smoothly narrowed to a continuously rounded apical margin, entire surface moderately strongly and densely punctured and variably cross-rugose, striae variably impressed and continued to the apex, the first and second deepened and diverging apically and 3-5 often united behind the middle. Legs slender and moderately long, the femora visible in normal setting, tibiae only weakly thickened towards the apex. Tarsi 5-segmented, pro-tarsi  short with segments 3 and 4 weakly lobed below, basal segment of middle and hind tarsi much longer than the rest, segment 3 of hind tarsi at least twice as long as broad. Claws smooth and lacking a basal tooth. Males may be distinguished by their more elongate distal antennomeres and by the presence of a transverse impression behind the clypeus.

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Hylis olexai 1