Heterocerus flexuosus Stephens, 1828
POLYPHAGA Emery, 1886
BYRRHOIDEA Latreille, 1804
Heterocerus Fabricius, 1792
This species is generally associated with coastal saline or brackish water habitats but there are inland records scattered across Europe, mostly from salt pits or workings but sometimes where the substrate is naturally salty. The species occurs around the coasts of Europe; it is generally very local and rare in the south but more common in the north where it extends to the UK and, sporadically, to the Arctic Circle in Fennoscandia. Further east it is recorded from Turkey, Israel (since 1999) and Jordan and along shores of lakes and rivers in Kazakhstan, Tajikistan, Uzbekistan, Turkmenistan, Pakistan and Mongolia, and it has recently been recorded from Iraq, Syria and Saudi Arabia (Skalicky, 2014) In the UK it is almost exclusively coastal although there are a few records from the English Midlands near Leicester; there are scattered records from the coasts of England and Wales, including Anglesey, except for much of the north east and the West Country, and from Northern Ireland (near Belfast). The usual habitats are margins of brackish pools, estuaries and salt marshes with patchy vegetation on silty or sandy substrates, Adults have been recorded throughout the year except for November and December, they peak in abundance during June and it is likely that winter is passed in this stage. They live in colonies and spend most of their time burrowing among wet substrate, where they feed on algae and organic debris, but they become active and sometimes swarm on warm days when they may be seen in numbers on the surface. The biology is not known but is very likely to be typical of the family with breeding occurring in the spring and larvae developing among substrate. Sampling is easiest by searching among suitable substrate, they are easily flushed out by local flooding and the species has often been attracted to light, including UV black lights.
Heterocerus flexuosus 1
3.5-5.1 mm. Identified among our UK species by the unmargined pronotal base and smooth elytra. Head black or obscurely paler anteriorly, pronotum black with the anterior angles and sometimes the lateral margin reddish, elytra variable; typically black with extensive reddish markings but always with the lateral margins substantially black. Antennae dark with pale basal segments. Legs dark, including the entire tibiae, with pale tarsi. Dorsal surface pubescent, densely so on the head and anterior pronotal margin and doubled on the elytra; with dense short pubescence and much longer erect hairs. Our only other species with the pronotal base simple (not margined) is H. fossor Kiesenwetter, 1843 but here the elytra are microsculptured, the lateral elytral margins are pale and the middle and hind tibiae are abruptly reddish apically. The first abdominal sternite bears a stridulatory ridge (which can be obscured by the hind femora), this appears as an oblique line extending from the lateral margin at the base and ending towards the centre of the apical margin, it does not recurve towards the base. This last character will distinguish all Heterocerus from species of Augyles Schiodte, 1866.