Nacerdes melanura (Linnaeus, 1758)   The Wharf Borer
This species is commonly known as the Wharf borer because the larvae have been extensively recorded boring into timber wharf pilings, harbour and dock timbers and into wood generally around the high tide mark, it also, and more importantantly, bores into ships timbers and has been distributed widely around the coastal areas throughout the world (Vite, 1953); large outbreaks have occured around Europe, the United States, Canada, New Zealand and Tasmania etc. This spread has been successful because the larvae will tolerate long periods of immersion and high salinity (Vazquez-Albalate, 2003). The species has been recorded from a range of both hard and softwoods and infestations may go unnoticed for some time through being hidden or inaccessible eg in timber enclosed in metal or concrete. Adults occasionally occur outdoors and tend to be conspicuous as they emerge in numbers and may appear year after year. Although it occurs throughout the UK it is most common in the midlands and around the estuaries in the south and southeast; London and the Thames estuary have been notorious for the beetle (Hickin, 1975) and the NBN (July, 2009) shows a string of records along the south Welsh coast. The slender greyish-white larvae grow to 30mm and generally occur as infestations, mostly in softwoods (gymnosperms) but also in oak etc (it has also been recorded from Eucalyptus) which is damp or wet and undergoing fungal decay, it is generally thought to accellerate the breakdown of fungoid timber rather than to initiate it. The preponderance of coastal and estuarine records suggests a preference for saline conditions but the species is sometimes common at inland localities; Hickin states that the insect was common along the banks of the Birmingham canals and around the Avon at Stratford and 'very common indeed' on London bombsites where salt water was absent. It was common in damp London cellars and basements during the 1970's. Fisher (1936) records larvae in the base of telegraph poles where dogs have urinated and also in fence posts etc similarly saturated. Adults are active from April to October (Vazquez-Albalate), Joy states 'july to September, local, on old timber on the shore, sometimes inland' They usually emerge en-masse and may be found on flowers or among vegetation, they fly readily and may disperse widely, occasionally occuring at light. Although we have yet to record the species from Watford we found several specimens at Cowley, Middx to the south of us along the Colne valley during June 2009. On this occasion several males were seen to emerge from the base of a partly decayed (but mostly healthy) alder standing a few metres from the edge of a lake; after emrging from the wood they moved rapidly up and down the trunk a few times before falling to the ground and running rapidly under surrounding shrubs.

This large and distinctive beetle is unmistakeable although the cantharid Rhagonycha fulva and the cerambycid Phymatodes testaceous are superficially similar, in both cases the 5-5-4 tarsi of Nacerdes are diagnostic.

9-13mm. An elongate and parallel sided species, almost wholly testaceous or dark testaceous. Head widest across eyes whicch are emarginate along the front margin. Temples contracted to base. Mandibles long and prominent, bifid at apex. Surface, including clypeus and labrum, finely punctate and pubescent, somewhat dull. Last segment of maxillary palps elongate, gradually widened to apex and sinuate on outer side before apex. Antennae 12 segmented in male, 11 in female, second segment small, about half as long as third. Pronotum slightly transverse; cordiform, broadest behind front margin and without lateral borders. Front margin raised, hind margin finely bordered. Surface finely punctured and with fine recumbent yellow pubescence. Elytra proportionally very long, about four times longer than pronotum, testaceous with apex darker. Pubescence short, dense and backwardly recumbent; obliquely so near suture, straighter towards lateral margins. Each with four fine longitudinal costae which extend into apical quarter, the third may be variously obliterated. Apex rounded. Legs testaceous to almost black; long and slender. Protibiae with a single spur on inside edge, meso and metatibiae with two well developed spurs on inside edge at apex. Tarsi 5-5-4, penultimate segment bilobed. Claws not toothed. Underside mainly black.

Description from 2 males at X10

Fisher, R.C. 1936. The habitat of Anoncodes melanura Ent.Mon.Mag. 72:41-42
Vazquez-Albalate, X. 2003 European fauna of Oedemeridae. Argania ,2003
Vite, J.P. 1953 Die Holzzerstorenden insekten Mitteleuropas. Munsterschmidt. Gottingen