RHYNCHITINAE Gistel, 1848
These distinctive weevils occur on trees or shrubs, where they develop in fruits, stems, buds or leaf rolls. They are most abundant in spring and early summer.
Historically this group has been variously considered as a distinct family or as a group within the Attelabidae; we include it under a subfamily heading as the most recent analysis has justified it's inclusion alongside the Attelabinae as a subfamily of the Attelabidae, and this is how it should be considered. While the placement and ranking of some groups e.g. Auletini or Pterocolinae is tentative, the Rhynchitids as a group are distinct among the Curculionoidea both in general morphology and in detail. They are small beetles,<10mm, with quadrate to elongate elytra which are generally wider than the head and pronotum, they thus superficially resemble many Attelabids but are a much more uniform group, so much so that a familiarity with our UK fauna will allow the group as a whole to be recognized. With the exception of New Zealand and many Pacific islands, including Hawaii, the group is cosmopolitan with by far the greatest diversity in the Oriental, Southeast Asian, Afrotropical and Neotropical regions, and temperate faunas are generally small by comparison. About 1100 species are known from 60 genera and 8 tribes, although various classifications can be found in the literature, and of these the faunas of Europe, Japan and the United States include about 50 species each. The central European fauna includes 25 species of which 18 species in 9 genera and 3 tribes occur, or have been recorded from, the UK. The 8 tribes are variously divided into numerous sub-tribes and many systems will be found in the literature, similarly some groups have been classified as distinct families e.g. Auletinidae Desbrochers, 1908 and it is obvious that a final system remains to be devised. The tribes as outlined below tend to have rather discreet distributions.
Pterocolinae Lacordaire, 1865 is a New World group of uncertain placement but they are typical, if generally rather broad in appearance, of the family. About 20 species of 2 genera are known and all are Neotropical with one exception, Pterocolus ovatus (Fabricius, 1801), which extends into the United States. All are parasites of attelabid weevils; adults of both sexes enter newly rolled leaves and consume the eggs, so far as is known they feed exclusively on the eggs and many specific host-parasite associations are known. They are commonly known as Thief Weevils or Leaf Roll Thiefs. Such parasitic behaviour is not confined to this group e.g. the European cuckoo weevil, Lasiorhynchus sericeus Herbst, 1797, is a brood-parasite of Attelabus nitens (Scopoli, 1763)
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Auletini Desbrochers, 1908, sometimes considered as a distinct subfamily or family, includes 6 genera, or more depending on how some subgenera are considered, and has a worldwide distribution. Pseudodicranognathus Legalov, 2001 is Indian, Dicranognathus Redtenbacher, 1844 is Southeast Asian, and Minurus Waterhouse, 1824 and Pseudauletes Voss, 1922 are Neotropical. Both Auletes Schönherr, 1826 and Auletobius Desbrochers, 1869 are widely distributed and represented in Europe; Auletobius is a large and almost cosmopolitan genus of about 220 species of which a third are Australian. The group is not represented in the UK.
Minurini Legalov, 2003 includes a few species of the single Neotropical genus Minurus Waterhouse, 1842. Species are unusually elongate and slender with long legs and rostrum, superficially resembling species of Apionidae. Sometimes included in the Auletini.
Rhinocartini Voss, 1931. This very tentatively placed group includes 2 genera from Africa and Madagascar and a recently discovered genus from Socotra Island, Yemen. In appearance they are typical of the family.
Rhynchitallini Voss, 1960 sometimes included as a subtribe of the Rhinocartini, this tribe includes the single genus Rhynchitallus Voss, 1960 from China.
Eugnamptini Voss, 1930 is a large tribe of about 200 species in 20 genera distributed throughout the New World, and the southeast Palaearctic and Oriental regions. Only 4 genera are Palaearctic and the vast majority occur in eastern Asia and the orient with China being particularly speciose. Species are very typical of the family.
The remaining 3 tribes are represented in Europe including the UK and serve to illustrate the majority of the family:
Byctiscini Voss, 1923 is restricted to the Palaearctic and Oriental regions extending south to the Philippines and Sulawesi. The group includes about 12 genera in 3 subtribes and is predominantly eastern in distribution. Our two UK species of Byctiscus Thomson, C.G., 1859 occur throughout the Palaearctic region and are the most widespread of the 30 or so members of the genus, 2 further species of uncertain placement and sometimes included in the genus Rhynchites, B. auronitens Gistel, 1857 and B. bicolor Gistel, 1857, occur in Germany and this completes the European list.
Deporaini Voss, 1929 is Holarctic and Southeast Asian in distribution, extending south to New Guinea but absent from Australia and tropical Africa. The group is divided into 2 subtribes; Chonostropheina Morimoto, 1962 is monogeneric and includes 4 species, of which 3 occur in Europe. Deporaina Voss, 1929 includes 8 genera and is mostly eastern; 2 species of 2 genera occur in Europe including the UK, Caenorhinus megacephalus Germar, 1823 and Deporaus betulae Linnaeus, 1758, both are very widespread, occurring throughout the Palaearctic including Japan.
Rhynchitini Gistel, 1848 is a cosmopolitan group although with only a few species in Australia, Madagascar and New Guinea; the New World fauna includes about 160 species of which 45 are Nearctic. The Palaearctic fauna includes about 30 genera and more than 220 species with by far the greatest diversity in the east. Many genera are restricted to the eastern Palaearctic but the UK list, which includes 14 species of 6 genera, are very representative as in all cases they represent larger and widespread Palaearctic genera. Involvulus Schrank, 1798 includes 35 species in 4 subgenera; 2 European species I. cupreus Linnaeus, 1758 and I. icosandriae Scopoli, 1763 (=I. caeruleus DeGeer, 1775) extend to the UK while a third, I. pubescens Fabricius, 1775 is widespread on the continent, all occur throughout Asia. Lasiorhynchites Jekel, 1860 includes 10 species in 4 subgenera, 6 occur in Europe and 2 extend to the UK. Neocoenorrhinus Voss, 1952 includes 13 species in 3 subgenera, 8 occur in Europe and 4 extend to the UK. Rhynchites Schneider, D.H., 1791 includes 18 species in 2 subgenera; 8 occur in Europe and 2 Palaearctic-wide species extend to the UK. The single species of Tatianaerhynchites Legalov, 2002 is a widespread western Palaearctic native and is common throughout Europe including the UK. Temnocerus Thunberg, 1815 includes 13 species, 4 occur in Europe of which 3 extend to the UK.
With the exception of the thief weevils the vast majority are known to be phytophagous and in Palaearctic species most develop on trees and shrubs with only very few consuming herbaceous plants. Females generally attack plants to promote decay which will facilitate larval development; in many species the larvae develop communally among a covering of decaying shoots and leaves, the plant having been attacked by the female beforehand, in Caenorhinus the leaf is petiole is partly severed and so withers and falls while the larva mines the epidermis, this is taken a stage further in Deporaus and Byctiscus where the female rolls the leaves which remain on the tree through the summer while the larva feeds inside. The female Temnocerus chews a hole in an unopened leaf bud and inserts an egg; she then chews around the base of the bud so that it will fall prematurely with the larva feeding inside. Some species e.g. Tatianaerhynchites develop in fruits which have been damaged by the female and so fall prematurely. These strategies ensure that the fully-grown larvae are in contact with the ground as most pupate in a subterranean cell, although some species e.g. of Lasiorhynchites oviposit under leaf buds on young twigs and larvae mine into the bark to develop, when fully-developed they simply fall to the ground and burrow. Some species have been pests of ornamental plants and fruit trees etc., Neocoenorrhinus germanicus (Herbst, 1797) has been an occasional pest of soft fruits, earning the common name of ‘strawberry rhynchitid’, Involvulus cupreus (Linnaeus, 1758) is an occasional minor pest of fruit trees. Some species of Rhynchites are sometimes serious pests in orchards in Europe and Asia; adults of R. auratus (Scopoli, 1763), the cherry-fruit weevil’ or ‘apricot weevil’ feed on flowers but will then oviposit in young fruits as they develop and very large populations of larvae can build up disfiguring fruits or causing them to drop prematurely.
The following description applies to the Rhynchitini and so includes most of the Palaearctic and world fauna, most other groups differ in small details e.g. species of Auletini differ in the antennae being placed close to the base of the rostrum and the elytra being randomly punctured with only a sutural stria being distinct, they are otherwise immediately recognized as members of the family.
The present family differs from most ‘true weevils’ in having non-geniculate antennae i.e. lacking an elongate scape, a feature also seen in several other curculionoid families; they differ from Nemonychidae and Anthribidae in lacking a distinct labrum, from Apionidae in the form of the mandibles and from Attelabidae by the mandibles being toothed externally as well as internally, the smooth inner margins of the tibiae and the separate claws which may be toothed internally or bifid, attelabid claws are fused at the base and simple. In all cases species of the present family should be distinct and obvious with a little experience. Rhynchitid larvae are also distinct from those of attelabids in having 3-segmented maxillary palps and distinct labium and postlabium; attelabid larvae have 2-segmented palps and the labium is fused to the postlabium. Adult rhynchitids are small to medium-sized beetles, ≤10mm, of very characteristic elongate form with a transverse head and long rostrum, near quadrate pronotum and parallel-sided elytra that are usually distinctly wider than the forebody. Some are black or bicoloured but most are metallic green, blue, coppery or bronze, usually with dark appendages. The dorsal surface is usually to some extent pubescent, sometimes finely so but often distinctly with long erect setae, sometimes doubled. Head usually transverse with prominent eyes that occupy much of the lateral margin, rostrum short to long, usually narrow and sometimes dilated towards the apex; in some this is dimorphic, being longer, finer punctured and sometimes more dilated in the female. Mandibles toothed externally although this may not be obvious as they tend to become worn in life, labial palps 3-segmented and inserted ventrally, sometimes atrophied, maxillary palps 4-segmented and usually rigid, labrum at least partly, and usually substantially, fused to the clypeus. Antennae without an elongate scape, basal segment not particularly enlarged or developed, funiculus 7-segmented, club 3-segmented and generally elongate, insertions dorsal or lateral, from near the base to near the apex, sometimes dimorphic; more basal in the female. Pronotum quadrate to transverse and narrower than the elytra, parallel to weakly rounded laterally, often constricted before the base or the apex and without lateral beads. Surface usually shiny and variously punctured, at most with only weak basal fovea, in males of Rhynchites with well-developed lateral spines. Scutellum small but usually visible, triangular to trapeziform. Prosternum short in front of rounded coxal cavities that are contiguous or nearly so and closed behind. Elytra usually straight-sided, parallel or weakly narrowed to the base or apex, shoulders prominent and usually right angled, usually with distinct punctured striae, if randomly punctured the sutural stria is generally distinct at least towards the base, often with a scutellary striole. Epipleura usually well-developed, at least in the basal half and often completely. Pygidium often partly or entirely exposed. Abdomen with 5 visible sternites, the basal 2 variously fused. Legs generally long and robust, pro- and meso-coxae round, meta-coxae transverse, meso- and meta-coxae variously separated. Trocanters small and triangular; obliquely attached to the femora and generally hidden within the coxa-femur junction. Femora robust and usually smooth, in male Deporaus the meta-femora are widely expanded. Tibiae long and stout, with 1 or 2 spines on the inner apical angle, sometimes this is dimorphic with males having a single spine and females two. Tarsi 5-5-5; segments 1, 2 and 5 elongate, 3 widely lobed and 4 small, sometimes they appear 4-4-4 as the tiny fourth segment is hidden within the lobes of the third. Claws free and sometimes toothed internally or bifid apically. Larvae are short and wide, strongly curved and often fusiform, the head is generally retracted into the thorax, bears 1- or 2-segmented antennae and either lack ocelli or have only one either side. They are legless and the abdominal segments divided into pleats by deep transverse grooves.