BOTHRIDERIDAE Erichson, 1845
Teredus cylindricus is a very local nocturnal saproxylic while the remaining species are subterranean and rarely encountered.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
Around the World
This family presently includes about 400 described species in about 40 genera and four subfamilies but many more await description, especially from tropical areas where the diversity is greatest, and the classification is by no means settled; the tribal limits are only poorly defined and some larger genera have been used as ‘dumping grounds’ for many species, and some genera may be confused through synonymy. Some groups have previously been included as distinct subfamilies or tribes of the Colydiidae or Cerylonidae; the Anommatinae were included as a subfamily of the Latridiidae before being transferred to the Colydiidae and then split off to form a part of the present family. Overall there is no single feature to distinguish the family and morphologically they are very similar to some members of the Colydiidae. The family is very diverse and includes mostly small or very small, flattened to cylindrical species, the majority of which are adapted to a saproxylic or subterranean lifestyle. They are a cosmopolitan group with most species occurring in old world tropical regions; by comparison the new world regions are poorly represented.
The Anommatinae Ganglbauer, 1899 includes about 150 species in 3 genera. Anommatus Wesmael, 1835 is an old world genus of about 120 species, many of which are Palaearctic in distribution; the widespread A. duodecimstriatus (Muller, P.W.J., 1821) is notable in having spread and become established in North America, Chile, Australia and New Zealand through unintentional introductions. Abromus Reitter, 1876 includes about 30 western Palaearctic species, most of which occur in the west of Europe and northwest Africa. Kocherius Coiffait, 1984 includes the single Palaearctic species K. perpisillus (Coiffait, 1984). All species are tiny, generally <2mm, elongate, parallel-sided and rather flattened, most are wingless and either lack, or have very reduced eyes. They are all drab insects, orange to black, with the dorsal surface variously punctured and either very finely pubescent or glabrous, all have a compact antennal club and short legs. They occur in compost and among decaying vegetation
generally, and many species are subterranean being associated with roots and tubers, some occur among the surface soil beneath damp logs etc. Very little is known of their biology but both adults and larvae generally occur in the same situations. Two species of Anommatus occur in the U.K., A. duodecimstriatus and A. diecki Reitter, 1875.
The Xylariophilinae Pal & Lawrence, 1986 includes 3 species of Xylariophilus Pal & Lawrence, 1986, a genus widespread through Oriental and Australasian regions and known to include several undescribed species from various Pacific Islands.
The Teredinae Seidlitz, 1888 is sometimes divided into 2 tribes. The Sysolini Slipinsky, 1985 includes the single genus Systolus Grouvelle, 1910 with 2 described species, from Vietnam and India, but there are several others known from various tropical regions. The Sosylopsini Dajoz, 1980 includes only the Madagascan Sosylopsis geayi Grouvelle, 1910 but the subfamily also includes several other genera of more doubtful placement; the monotypic Rustleria Stephan, 1989 includes R. obscura Stephan, 1989 from Arizona, Teredomorphus Heinze, 1943 includes 2 old world tropical species, and Teredolaemus Sharp, 1885 about 20 mostly African species although a couple are more widespread e.g. T. barbieri Dajoz, 1980 occurs in Vietnam, and T. bottcheri Heinze, 1943 in the Philippines. Teredus Shuckard, 1840 includes 4 Palaearctic and African species with T. cylindricus Olivier, 1790 extending into the U.K. Oxylaemus Erichson, 1845 is a widespread Palaearctic and Asian genus with a single species O. californicus Crotch, 1874, occurring in the Nearctic region. The Palaearctic species O. cylindricus (Creutzer in Panzer, 1796) and O. variolosus (Dufour, 1843) extend into the U.K.
Bothriderinae Erichson, 1845 includes the majority of the species; more than 200 in about 30 genera. It is a cosmopolitan group with some large and widespread genera although primarily tropical and only poorly represented in temperate regions, more especially so in Europe. Sometimes split into two tribes, although it seems without universal acceptance; the Deretaphrini Horn, 1878 includes 3 genera. Asosylus (Grouvelle, 1908) includes 7 species from Southeast Asia, The Philippines and New Guinea. Sosylus (Erichson, 1845) includes more than 50 species and is almost exclusively African although a single species, S. signatus Hinton, 1936, is recorded from Mexico. Deretaphrus (Newman, 1842) includes more than 30 Australian species with at least one, D. fossus Newman, 1842, endemic to Tasmania. The group is not represented in Europe, at least not naturally. The remainder are included in the Bothriderini (Erichson, 1845). The majority are old world groups but a few are exclusively Neotropical e.g. Prolyctus Zimmerman in Leconte, 1869 with about 10 species and Lithophorus Sharp, 1884 with 5 species. Many genera are widespread across Southeast Asia, the 6 species of Erotylathris Motschulsky, 1861 exclusively so, and some have a wider distribution; Pseudobothrideres (Grouvelle, 1908) includes about 20 species spread across Asia, including India, and Africa, while the large genus Bothrideres (Dejean, 1835), with more than 60 species, occurs mostly in Australia and the Far East and includes some endemics e.g. B. fryeri Grouvelle, 1819 from Aldabra, and B. signatus Grouvelle, 1896 from Madagascar, and B. geminatus (Say, 1825) occurs in the United States. The 36 species of Ascetoderes Pope, 1961 is similarly Australian and Southeast Asian. The small genus Triboderus Grouvelle, 1894 is widespread in Asia and Africa and includes 4 species. Antibothrus Sharp, 1885 includes 6 species; 2 from Japan, 1 from Russia, 2 African species and 2 Madagascan endemics. Some groups are exclusively African e.g. the monotypic Shekanus Pope, 1961 from Ghana, and Pseudantibothrus Pope, 1955 with 2 species. The single species of Pseudososylus Grouvelle, 1900, P. colydioides Grouvelle, 1900, occurs in the Congo. Machlotes Pascoe, 1863 includes 15 African species with at least one, M. vadoni Dajoz, 1980, endemic to Madagascar. The monotypic Roplyctus Pope, 1953 includes the Madagascan endemic R. castanescens (Fairmaire, 1899). The subfamily is not represented in the U.K. but several are recorded from Europe including the central European Bothrideres bipunctatus (Gmelin in Linnaeus, 1790).
The Anommatinae form a distinct group within the family, they develop among decaying organic material, are apterous and have reduces eyes or are eyeless. Many are soil living and rarely encountered but sometimes occur among litter or in the soil under logs etc, and they occasionally swarm. Biologically they are little-known but the larvae generally occur in the same habitats as the adults. Some species of Anommatus are thought to be parthenogenetic. Members of the other subfamilies are saproxylic and many have specialized lifestyles. Species of the Teredinae and Xylariophilinae are thought to be entirely mycophagous with a normal larval development (see below); Teredinae larvae feed on spores in the galleries of Scolytids and other wood-borers while those of Xylariophilus develop within the fruiting bodies of Ascomycetes. Adults are nocturnal, occurring around damaged wood on the surface of trunks and logs etc. and may occur in large numbers. Species of Bothriderinae are ectoparasitic on the early stages of other saproxylic insects, having hypermetamorphic larvae with first instar triungulins that are highly mobile and search through galleries or under bark for suitable hosts. This lifestyle has been known of for decades but is still little understood; the Nearctic Deretaphrus oregonensis Horn, 1872 earned the common name of ‘Buprestid destroyer’ from the periodic proliferation of its larvae in the burrows of buprestids and other saproxylic coleoptera. The triungulin latches onto its host and begins feeding, soon growing and moulting into a normal grub-like second instar that will develop on the host. Fully grown larvae produce silk cocoons, either attached to the remains of the host or a short distance away in the gallery, in which to pupate. A wide range of hosts have been recorded including various Hymenopotera larvae (Apidae and Xiphydriidae), and most families of saproxylic coleoptera e.g. Buprestidae, Bostrichidae, Ptinidae and Cerambycidae. Some Bothrideres and Sosylus are associated generally with Scolytids and Platypodids, and some Sosylus may be host species-specific.
Bothriderids vary enormously in general morphology and so it is impossible to summarize a typical specimen; the size varies widely from about 1.5mm to 12mm, as in some of the larger Deretaphrus species, but the majority are small, <5mm. Generally they are convex and very elongate, up to 4X longer than wide but in all cases at least 2.5X, with the head visible from above, rather short antennae and robust, usually well-developed legs. Most are discontinuous in outline and distinctly constricted between the pronotum and the elytra, more especially so where the pronotum is shield-shaped, as in some Deretaphrus and Bothrideres, and most strongly so where the pronotum tapers towards a broad elytral base with prominent shoulders, as in Ascetoderes musivus Pascoe, 1862. They are mostly drab yellow to black in colour and rarely metallic although occasionally distinctly patterned e.g. Xylariophilus bicoloripennis Pal & Lawrence, 1986, and some tropical species have distinct red or yellow maculae. Most are glabrous or very finely pubescent but there are exceptions e.g. Teredolaemus setipennis Pope, 1952 has sparse but very long pubescence to the head, pronotum and elytra. Most have well developed eyes which vary from convex and prominent e.g. in some Bothrideres Haldeman, 1843 and Ascetoderes Pope, 1961, to small and flat as in Deretaphrus Newman, 1842, and in the Anommatinae they are reduced or absent. The labrum is often reduced or apparently absent and the mandibles are robust and bifid. The antennae are 9-11 segmented and usually have a 3-segmented club but this varies; in some it is 2-segmented, e.g. Teredus Shuckard, 1840 and in e.g. Oxylaemus Erichson, 1845 there is a single large segment. Occasionally the club may be loose and only gradually expanded e.g. in Deretaphrus. The antennal insertions are generally visible in front of the eyes and behind the mandibles. In most cases the eyes are placed laterally between distinct temples and cheeks. Vertex flat to strongly convex, usually distinctly punctured and often dull due to strong microsculpture. The pronotum varies enormously; generally elongate and sometimes, e.g. in Anommatus, as long as the elytra, although there are exceptions e.g. in Dastarchus Walker, 1858, and usually lacking lateral borders; parallel to distinctly rounded and broadest from the middle to the anterior angles. The margins are generally smooth although in some groups e.g. Ascetoderes Pope, 1961 they are distinctly toothed. The anterior and basal angles are often simply rounded or weakly angled but in some groups e.g. Deretaphrus and some Bothrideres they are sharply angled, and in some e.g. Ascetoderes taeniatus Pascoe they are produced and toothed. The surface is generally flat and even but there are many exceptions; in Dastarchus it is very heavily sculptured overall, and in some e.g. Deretaphrus fossus Newman, 1842, there are distinct basal fovea, and in others longitudinal furrows or depressions which may be extensive. The punctation varies from very fine to very strong even within a single genus e.g. among the species of Oxylaemus. The pro-coxal cavities are open behind and often laterally, and separated by a distinct process, the prosternum being broadly visible anterior to these. The pro-coxae are variously shaped but overall rather rounded and flattened; the trocanters are small and often not visible. The meso-coxae are round and distinctly separate. Scutellum usually visible. The elytra are very variable ranging from simply cylindrical and smooth e.g. in Teredolaemus leae Grouvelle, 1908, to punctato-striate as in Oxylaemus or longitudinally carinate, sometimes exaggeratedly so e.g. in Prolyctus Zimmerman in Leconte, 1869, or roughly sculptured and scaled as in Dastarius kurosauai Sasaji, in some Antibothrus they are smooth but have several prominent longitudinal carinae in the basal half. The pubescence varies from very fine, almost glabrous, to fine and dense, as in some Bothrideres, or sparse and long. The suture is usually simple although sometimes has a raised margin or carina, and the elytra usually meet to the apex although in some Teredolaemus species they diverge apically. The elytra always cover the abdomen. Tarsi 4,4,4 except in Anommatinae where they are 3,3,3. The abdomen has 5 free ventrites.
Without a great deal of experience and knowledge the members will be very difficult to identify, and more especially so as in the field where, even in the U.K., there are many groups with superficially similar species e.g. Monotomids, Cryptophagids, Laemophloeids and Silvanids etc., and running the species through family keys will not be straightforward even with our limited fauna where large sections e.g. Chrysomeloidea, Curculionoidea and Adephaga can be ignored; elements of good luck and sharp intuition will be needed e.g. when trying to decide the tarsal formula of Anommatus. On the other hand our few U.K. species are distinctive and so can be ‘learned’ from pictures on the internet and from publications etc. as all have features that will readily identify them, at least to the generic level, and so the use of a key seems a rather pointless and frustrating process, as a confidence boost the species can be worked backwards through family keys in order to eliminate other groups, or otherwise.