Tillus elongatus (Linnaeus, 1758)

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POLYPHAGA Emery, 1886

CLEROIDEA Latreille, 1802

CLERIDAE Latreille, 1802

TILLINAE Fischer von Waldheim, 1813

TILLUS Olivier, 1790 

This is a locally common species throughout Europe, except for the extreme west, from the northern Mediterranean to the UK and southern Scandinavia and east to the Caucasus and much of western Russia; in the UK it occurs in the south and east of England and there are scattered records further north to Cumbria and from Ireland. The typical habitat is old established woodland and parkland with mature deciduous trees in various stages of decay; they occur on a range of trees e.g. oak, maple and lime but beech seems to be preferred and they will typically inhabit old and dry trunks devoid of bark and exposed to the sun, they rarely occur on fallen timber. Adults have been recorded feeding on honeydew and the pollen and nectar of flowering lime and other trees although they only rarely occur on flowers, and they are primarily predatory on other saproxylic insects and their larvae, they are most commonly associated with the Ptinid, Ptilinus pectinicornis (Linnaeus, 1758) but have also been observed predating other species e.g. Hadrobregmus denticollis (Creutzer in Panzer, 1796). They occur from May to August and are diurnal as well as nocturnal; during the day they hunt on sun-exposed surfaces and on hot afternoons may swarm in flight around the tops of old stumps, generally among swarms of Ptilinus, at night they hunt on the wood; moving rapidly and exploring the borings of other insects. In our experience females by far outnumber the males which tend to be much less active and conspicuous. From early May they emerge from the wood at night; they bore a circular emergence hole which is quite distinctively larger than the abundant Ptilinus emergence holes which are usually present, and they partially emerge, remaining for some time head-first half way out of the hole before finally escaping. Although very local they are usually abundant where they occur and once established a colony may persist for many years, this was the case in our local park but despite the large numbers we regularly observed we never found them mating. Oviposition occurs from May when eggs are laid in the chambers of other wood borers, and at this time the females may be observed quickly exploring a series of holes before deciding to insert the abdomen and oviposit, this behaviour continues over a long period into the summer. Larvae predate those of other insects, mostly within the galleries but on warm nights are active under bark or on the surface of denuded wood.

7.0-10.0mm. A very distinctive species which should not be confused with any other, males are entirely black while females have a red pronotum although rarely this may be to some extent darkened, and under very strong light e.g. powerful camera flashlights, some males will be seen to have pale longitudinal stripes of red to the elytra, and some females have a pale lateral macula near the middle. Entire dorsal surface with sparse long pubescence which tends to be erect on the head and pronotum and recumbent on the elytra. Head evenly convex between weakly convex and anteriorly emarginate eyes, slightly wider than the pronotum and with long, serrate antennae. Pronotum elongate, widest in front of the middle and constricted in the basal third, surface finely punctured and transversely wrinkled; more strongly so in the male. Elytra very elongate, with well-developed shoulders and strongly punctured striae which fade towards the apex, dilated beyond the middle in both sexes but usually more strongly so in the female; apices continuously rounded and either covering the abdomen or leaving one or two segments exposed. Legs long and slender; entirely black but for the paler claws, tarsal segments 2-4 bilobed, claws bifid with a strong basal tooth.

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