ERIRHININI Schönherr, 1825
All species are found in wetland habitats; mostly marginal substrate, but also on aquatic and nearby vegetation.
In following the latest Palaearctic checklist we have included this group as a tribe within the Brachycerinae Billberg, 1820, although it will be found variously as a distinct family within the Curculionoidea (as in the latest UK checklist (2016)), a subfamily of the Curculionidae or, so far as the UK species are concerned, a series of tribes within an expanded Erirhininae. The modern system, and one which has been in use for some time in the United States, places the group within Brachycerinae (dae) Billberg, 1820, a very distinct group within the Curculionidae, 1820, either as a subfamily as variously accepted in America, or as one of a series of tribes, which has recently been adopted for the Palaearctic fauna. The subfamily is cosmopolitan and well-represented in most regions; the North American (in the widest sense) list includes about 200species, South America about 250, Eurasia about 900 of which about 450 are Palaearctic, Australasia about 250 and Africa, which is particularly diverse, almost 1000. The situation is not resolved; in some systems the Brachyceridae is a distinct family comprising 2 subfamilies; Brachycerinae Billberg, 1820 includes the vast majority of species, more than 5000 in more than 300 genera, while the Cryptolarynginae Schalkwyk, 1966 includes 6 species in 2 genera, one of which is Palaearctic. In the most recent system the curculionid Brachycerinae is divided into a series of tribes. The justification for defining the group (Erirhinini) as a distinct family was based on the form of the aedeagus which, being ‘pedotectal’ and therefore representing a more primitive form, was thought to reflect a more primitive stage of evolution for the group as a whole, and so it was placed phyllogenetically before the ‘proper’ or more advanced of the curculionoid weevils. As such, and because of the immense variety of morphology present in even a limited diversity such as we have in the UK, there is no single structural feature, or even easily defined group of structural features, that will distinguish the group from the other subfamilies of the Curculionidae. Of course they will key out, admittedly as several distinct forms because any particular character or even group of characters is present in our other curculionid weevils, and this has been done successfully in several recent keys (see further reading below), but a general description of the group
will have to accommodate so many exceptional characters that it becomes rather pointless when viewed against our wider fauna, and for this reason we have included a key to the UK species in order to illustrate some of this morphological diversity; the key will work to identify the species, in a simplified way, but its main function is to illustrate the wide range of characters exhibited by the group in the UK. The relatively small size of our fauna will be realized from the following discussion which attempts to compare the UK list with the wider Palaearctic fauna but nonetheless it is fairly representative of the Holarctic fauna as a whole, and once familiar there is a certain and rather distinctive feel about the group and so many foreign species will be readily placed.
Brachycerinae is represented in the Palaearctic region by 6 tribes, and beyond this there are at least 7 further genera of uncertain placement.
Bracycerini Billberg, 1820, is present as the subtribe Brachycerina Billberg, 1820 and includes the single large genus Brachycerus Olivier, 1789, about 400 species are known, of which about 350 occur in mainly arid regions of Africa, including the Middle East and Madagascar, and about 50 are known from the south-western Palaearctic region, mostly from the Mediterranean, Caucasus and Central Asia. The wider world fauna includes 6 genera and almost 700 species and is widespread also in Asia, Australasia and Africa. None occur in the UK.
Cryptolaryngini Schalkwyk, 1966 is monogeneric; Perieges Schöenherr, 1842 includes 2 Asian and 1 European/North African species, none of which have been recorded from the UK.
Erirhinini Schöenherr, 1825 is represented by 2 subtribes.
Ocladiina Lacordaire, 1865 includes 7 genera and about 40 species, it is a widespread group throughout Eurasia, Africa and the Oriental regions but is not represented in the UK.
Erirhinina Schöenherr, 1825 includes 14 widespread Palaearctic genera, of which 5 are represented in the UK. Of the 5 species of Grypus Germar, 1817 3 are restricted to eastern Asia while 2 are widespread throughout the region; G. brunnirostris Fabricius, 1792 occurs throughout Europe and much of Asia, while a single species, the Holarctic G. equiseti Fabricius, 1775 extends also to the UK. Notaris Germar, 1817 includes 18 Palaearctic species, most are Asian but of the 5 very widespread Eurasian species 3, including the Holarctic N. aethiops Paykull, 1792,extend to the UK. Procas Stephens, 1831 includes 9 mostly European species. Two species occur in the UK and both have a rather restricted distribution; P. picipes Marsham, 1802 occurs in north and western Europe while P. granulicollis Walton, 1848 is local in mainland UK and known otherwise only from Spain. Of the 5 species of Thryogenes Bedel, 1884 1 is restricted to Asia while the others are widespread and extend to the UK. Tournotaris Alonso-Zarazaga & Lyal, 1999 includes 3 species of which 2 have restricted European and Asian distributions while T. bimaculata (Fabricius, 1787) is Holarctic occurring throughout Europe, Asia and North Africa and extending to the UK.
Hinasthlophallini Zherikhin, 1991 is monotypic including the single Asian species Himasthlophallus flagellifer Egorov & Zherikhin, 1991.
Raymondionymini Reitter, 1913 is a mostly European group.
Tanysphyrini Gistel, 1848 includes 6 genera and 11 species. The single member of Stenopelmus Schöenherr, 1835, the widespread western Palaearctic and Nearctic S. rufinasus Gyllenhal, 1835, which extends to the UK, was formerly included in the separate tribe, Stenopelmini Leconte, 1876. The tribe is further represented in the UK by 2 species of the Holarctic genus Tanysphyrus Germar, 1817.
With the exception of the 2 species of Procas which appear to be monophagous on various Fumariaceae, our UK members of Erirhinini are associated with wetland habitats; only Grypus equiseti, which develops on various species of Equisetum (horsetails), is at all likely to occur away from marginal habitats, and 2 genera, Stenopelmus and Tanysphyrus will need to be looked for by sweeping floating vegetation. Our species are generally associated with particular plants although many will be found by general sweeping and searching the surface of moist substrate, especially in early summer when marginal soil is starting to dry out vegetation is dying back. Tanysphyrus lemnae is usually found among Lemna in still and stagnant water, whereas T. ater, a recent discovery in the UK, is associated with Ricciocarpos nutans on the continent. Stenopelmus rufinasus, an established invasive Nearctic native, occurs on Azolla filiculoides (water fern). Species of Thryogenes may be found by searching around the base of sedges, reeds and rushes, and we have found several under dry matted algae among gravel on a dry spring bed. Notaris occur around well-vegetated still water margins and may be swept from various Typhaceae and Cyperaceae, or found among leaf-litter or under debris in marginal situations, often in numbers.
Our species are all rather elongate and parallel-sided, least so in Stenopelmus, with broad shoulders that are wider than the base of the elytra, least so in Tournotaris, with a relatively small head and quadrate to slightly elongate pronotum and evenly convex and punctato-striate elytra. With the exception of Grypus they are drab brown to grey, sometimes with a dense covering of scales which may form patterns. With the exception of Tournotaris all have long and slender appendages, all have unarmed femora and 5-segmented tarsi but the fourth is diminutive and so they appear 4-segmented, with the exception of Stenopelmus all have the third strongly bilobed; in Tanysphyrus the lobes are as long as the fifth segment. Tarsal claws free and smooth, lacking a basal tooth.
A key to the UK species is available HERE.