Phylan gibbus (Fabricius, 1775)

This halobionte species occurs sporadically from the Atlantic coast of Spain north to the UK, southern Fennoscandia and Russia, there are older inland records from Europe but these are thought to be erroneous, and over much of its range populations have become fragmented and it is suspected to be in decline due to human exploitation of coastal habitats, in the UK it is locally common around the coast of England from the Humber estuary to Cumbria, including Anglesey and Man, and there are a few inland records from East Anglia. Adults are present year-round, they occur on sandy and gravel beaches, they are flightless and nocturnal, scavenging among tussocks and stranded seaweed by night and remaining beneath the surface at the foot of dunes or under debris by day although on the hottest days they may be found active in numbers on dry substrate above the strand-line. They may be sampled by sieving sand etc. or searching among tussocks during the day, by pitfall trapping or by searching at night, and when found they are usually present in numbers. Mating occurs from May and larvae develop among buried decaying vegetable matter, they often occur alongside the adults and when exposed will quickly burrow back into the substrate, there is a single generation each year with pupation occurring from August and new-generation adults appearing from September, these will go on to overwinter in the soil high up on the beach and become active early the following year.

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The large size, entirely dark colouration and general habitus are very distinctive, only Opatrum, which is similar in size and occurs in the same habitats, might casually be mistaken for this species but here the elytral sculpture is very different. 7-9mm. Elongate-oval and rather parallel-sided. Head transverse, smoothly rounded and emarginate anteriorly, densely and quite strongly punctured, laterally wrinkled beside weakly convex eyes that are divided by the expanded clypeus. Terminal maxillary palpomere expanded and truncate, antennae long and narrow, the segments elongate at the base becoming quadrate or slightly transverse towards the apex. Pronotum transverse, broadest about the middle and strongly sinuate before perpendicular posterior angles, anterior angles weakly produced, surface finely and densely punctured, and wrinkled towards the lateral margins. Elytral base only slightly wider than the base of the pronotum, laterally sinuate behind the shoulders, broadest in the apical third then narrowed and sinuate to a continuously rounded apical margin, surface variously rugose with strongly-punctured striae and slightly convex and densely punctured interstices.   Legs long and robust, middle and hind tibiae curved, with numerous short spines externally and, in the male, dense long pale setae internally. Front tibiae strongly expanded to a truncate apex, all tibiae in both sexes with a pair of short spurs at the inner apical angle. Tarsi 5-5-4, all segments narrow in the female; male with pro-tarsal segments 1-3 dilated, the third partially enclosing the small fourth segment.