Tarsostenus univittatus (Rossi, 1792)
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POLYPHAGA Emery, 1886
CLEROIDEA Latreille, 1802
KORYNETINAE Laporte, 1836
Tarsostenus Spinola, 1844
Thought to be native to Australia, where it is widespread and common around Eastern and Western coastal regions, this species has become established in warmer regions worldwide, including many oceanic islands, and it often occurs or becomes locally and temporarily established in temperate regions, including much of Europe, mostly as a result of the trade in timber and timber products. In the UK there are records from Southern and North-Eastern England; it is very rarely recorded and these specimens are generally considered to be from timber imported from warmer regions. Adults have been recorded throughout the year in warmer regions, usually peaking in spring or summer, and they are likely to occur wherever suitable prey is common, both in the wild and under artificial conditions. This is refelected in cooler regions where they might occur at any time. Typical natural habitats are broadleaf woodland and wooded scrub etc.; in Europe the adults often occurring under decaying bark or among wood in old oaks and beeches but they have been recorded from a range of trees in suitable states of decay. Both adults and larvae predate other insects and their larvae and both stages are thought to be specialist predators of species of Lyctus; adults often hunt on the surface at night while larvae spend most of their time in Lyctus borings. Adults also visit flowers of various trees and shrubs in the spring in order to hunt other insects, sometimes in numbers and usually in the evening but sometimes also in bright sun. It is possible that the species may breed in the UK as females may lay up to 100 eggs and these require a minimum developmental temperature of only 14°C while larval/pupal development requires at least 15°C (under artificial conditions.) Whether the species can otherwise survive our climate is not known, and when it appears in numbers they are likely to have originated from imported timber products.
3-5 mm. Elongate and narrow, body with fine erect pale pubescence, shiny black to dark reddish-brown, sometimes with a faint bluish reflection, elytra each with a pale transverse band behind the middle, these vary and usually do not met at the suture, antennae pale brown at the base and usually becoming darker apically, legs pale to dark brown. Head slightly broader than the anterior pronotal margin, rather flat and moderately strongly but not densely punctured between large and weakly emarginate eyes, labrum strongly emarginate, sometimes bilobed. Terminal maxillary and labial palpomere elongate, dilated and obliquely truncate. Antennae inserted laterally in front of the eyes, long and slender with a loose 3-segmented club. Pronotum elongate, broadest behind the middle and narrowed to obtuse posterior angles, anterior half or so almost parallel-sided, anterior angles rounded and apical margin straight, lateral margins not bordered, surface often longitudinally depressed medially, strongly punctured; sparsely so on the disc but more densely so laterally. Elytra long and slender, usually weakly dilated behind the middle, shoulders sloping and apical margins separately rounded, explanate margin broadening beyond the middle, striae regular and strongly punctured from the base, becoming weaker after the middle. Legs long and robust; femora unarmed, tibiae slender. Tarsi 5-segmented, basal segments lobed, terminal segment long and slender; basal segment of hind tarsi diminutive and hidden beneath the second segment. Claws smooth and not toothed at the base.
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The only confusion among our UK species might be with Paratillus carus, which is similarly slender and marked, but here the terminal maxillary palpomere is slender and only slightly widened from the base.