Tetrops Stephens, 1829
POLYPHAGA Emery, 1886
CHRYSOMELOIDEA Latreille, 1802
LAMIINAE Latreille, 1825
TETROPINI Portevin, 1927
T. praeustus (Linnaeus, 1758)
T. starkii Chevrolat, 1859
Tetraopini is a cosmopolitan tribe of more than 200 species in 15 genera, most of which occur in the Asian, Australasian and Ethiopian regions and less so in the Nearctic. Only the single genus Tetrops Stephens, 1829 occurs in Palaearctic Asia and Europe. Tetrops includes about a dozen species and is primarily Palaearctic in distribution with only a single adventives species in the Nearctic. In general members of the tribe are small and more or less parallel sided longhorns with the head almost vertically inclined anteriorly, they are robust for their size and with antennae shorter than the body. The eyes are completely divided and the palps are short with oval segments. The pronotum is cylindrical, or nearly so, and generally constricted towards the apex and/or base, the lateral margins are smoothly sinuate and lack projections, teeth or spines and the surface is usually pubescent and finely punctured. The elytra are randomly punctured, rounded or truncate apically and they completely cover the abdomen. The claws are usually strongly toothed at the base.
The genus Tetrops includes, among others, the following species:
T. gilvipes Falderman, 1837 from Europe, Central Asia and Iran.
T. hauseri Reitter, 1897 from Southern Asia and China.
T. mongolicus Murzin, 1977 from Eastern Siberia.
T. rosarum Tsherepanov, 1975 from Mongolia.
T. warnckei Holzschuh, 1977 which is endemic to Italy.
T. starkii Chevrolat, 1859 from Europe, including the U.K, east to Ukraine.
Our two UK species are readily separated:
Apical elytral margin truncate or weakly rounded. Lateral margin of the pronotum with short and dense pale pubescence as well as the longer erect setae. Anterior tibiae of the male slender compared with the female.
Apical elytral margin with a small and blunt projection or tooth. Lateral margin of the pronotum with long erect setae but without the short white pubescence. Anterior tibiae of the male expanded towards the apex.
Tetrops praeustus 1
Tetrops starkii 1
Tetrops praeustus 2
Tetrops praeustus Linnaeus, 1758
This is the more common and widespread of the 2 species present in the U.K. It is distributed throughout England north to Cumbria although records are more scattered in the west and it is absent from much of Wales. The only island records seem to be from The Isle Of Wight. On the continent it is a widespread native occurring throughout Europe north to Southern Scandinavia and east through Russia to Mongolia. There are 3 subspecies; T. p. algiricus Chobaut, 1893 from Algeria, T. p. anatolicus Ozdikmen & Turgut, 2008 from Turkey and the widespread typical form. The species was introduced to North America and it is now widespread through the northern U.S.A. and Canada. In the U.K. adults occur from April or May to September depending upon the year. The typical habitat is wooded margins or clearings and parkland where they are active among shrubs and low vegetation e.g. honeysuckle, viburnum and blackberry etc. and they may be seen in flight around host trees or nibbling leaves and sometimes on umbel flowers or blossom etc. during warm weather. The eggs are laid singly among the bark on dead or damaged twigs and small branches of a wide range of hosts including oak, rowan, lime, elm, apple, hawthorne and ash etc. but the preferred host seems to be Pyrus malus. Newly hatched larvae feed initially within the bark before moving underneath and producing spiral-shaped galleries. Pupation occurs in early spring, or is sometimes delayed, in the outer layers of the xylem or under the bark and the adults eclose in the spring. The life-cycle is usually completed within a year but may occasionally take two.
Without experience this small and distinctively coloured species may be mistaken for a cantharid but the short legs and robust antennae should be decisive, the only real confusion should be with our other species, T. starkii, see below. 3-6 mm. Black with the front legs entirely, and all tibiae, yellow. The elytra are yellow with the apical region darkened (viewed under u.v. light the dark area turns a vivid metallic blue!) The entire body has long, pale setae-like pubescence, the lateral margins of the pronotum also with dense short, white pubescence which can be very difficult to see. The head is relatively large, transverse and deflexed, the vertex and frons sparsely and finely punctured. Antennae robust; reaching the elytral apex in the male and obviously shorter in the female. The pronotum is parallel and constricted in the basal third, the surface and the lateral margins uneven. All margins smooth, without teeth or projections. Slightly elongate in the male and slightly transverse in the female. Elytra subparallel and weakly constricted medially, with well-developed shoulders; much broader than the pronotal base, the surface with wide and shallow, random punctures. The apical margin is obliquely truncate with both angles rounded. Anterior tibiae of the male are more slender when compared to the female.
Tetrops starkii Chevrolat, 1859
This is a much more local insect than T. praeustus and has a smaller range; generally in central and southern Europe east to western Russia and Ukraine with only occasional and scattered records further north to southern Scandinavia and the central parts of England. In the UK the habitat is much as praeustus but it is very local and rare and records are scattered but there is a long-term colony in South Wiltshire. This species seems to be oligophagous, in the UK on Ash (Fraxinus L.) but on the continent also on Oak (Quercus l.) and other broadleaved trees where the adults are known to consume the leaves. Adults are active from May or June, they may be beaten or swept from foliage and they sometimes appear on blossom. Oviposition occurs among the bark of recently dead or damaged twigs and small branches of otherwise healthy trees and the larvae feed under the bark. Pupation in early or mid-spring produces adults in May and June. The life cycle is completed within a year.
The length of this species is the same as that of praeustus but it is generally a little broader and the elytra darker; the apex being more sharply defined and more extensively black. Very rarely specimens occur with the elytra entirely dark. The anterior tibiae of the male are distinctly widened. In the male the pygidium is trapeziform while in the female it is simply rounded.