MORDELLIDAE | uk beetles

MORDELLIDAE Latreille, 1802

Tumbling Flower Beetles

Includes mostly very local southern species, often found on flowers or around wood in hot weather.

POLYPHAGA Emery, 1886

TENEBRIONOIDEA Latreille, 1802

2-9mm

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Introduction

Adult Mordellids are a morphologically narrow and homogenous group readily recognized by the streamlined and convex form, the produced, style-like abdominal apex (actually the 7th tergum), and the form of the hind legs with flattened femora and oblique or horizontal ridges to the tibiae and tarsi. The world fauna includes about 1500 described species in about 115 genera, 5 tribes and 2 subfamilies, although the number of genera is likely to increase as the group is dominated by a few very large genera which have tended to be treated as a dumping ground over the 19th and 20th centuries. The Ctenisiinae Fransiscolo, 1951 includes a single species from South Africa which is distinctive in having pectinate antennae. The Mordellinae includes 5 very unequal tribes. Conaliini Ermisch, 1956 includes almost 20 species in 9 genera and is pantropical; 4 genera are Neotropical, 3 are African, a single genus is endemic to Sumatra, and Ophthalmoconalia Ermisch, 1968 includes 2 species, one from Thailand and one from Africa. Reynoldsiellini Fransiscolo, 1957 includes only the monotypic Reynoldsiella Ray, 1930 from Venezuela. Stenaliini Fransiscolo, 1956 includes 4 genera, 3 of which, including 16 species, are exclusively African while Stenalia Mulsant, 1856 includes more than 70 species from Africa, Asia, Europe and the Oriental region. Mordellistenini Ermisch, 1941 includes 38 genera and is cosmopolitan, the group includes the huge genus Mordellistena Costa, 1954 which, if some of the lists on-line are to be believed, includes more than 900 species, but some have been transferred to other genera. Most of the genera are small and there are many regional and island endemics, more especially so among Mordellistena. Some are widespread e.g. Mordellochroa Emery, 1876 with 8 species is Holarctic, Calyce Champion, 1891 with 9 species is Neotropical and African, and the 19 species of Dellamora Normand, 1916 occur throughout the Old World tropics, but many are localized; Xanthomorda Ermisch, 1968 includes 8 species from Papua New Guinea, and Neomordellistena Ermisch, 1950 includes about 25 African species. The 30 or so species of Falsomordellistena are mostly Oriental. Mordellini Siedlitz, 1875 is the largest group with about 60 genera and is dominated by 2 large genera, the cosmopolitan Mordella Linnaeus, 1758, with more than 500 species, and Gilpa LeConte, 1859 which is pantropical extending

into Asia, and like Mordella, includes many island endemics. Tomoxia Costa, 1854, with about 55 species, is cosmopolitan. Many genera are restricted to particular regions; the 4 species of Austromordella Ermisch, 1950 are Australian, Iberomorda Méquignon, 1946 comprises 2 European species, and many are endemic to Africa e.g. Neocurtimorda Fransiscolo, 1950 (13 species), Paratomoxia Ermisch, 1950 (9 species) and Stenomorda Ermisch, 1950 (5 species including a Madagascan endemic). Several genera are diverse in Africa but also extend to other regions e.g. Glipostenoda Ermisch, 1950 with more than 50 African and Oriental, and a single Nearctic species, and Mordellina Schilsky, 1908 includes 25 African and Asian species. More widespread genera include the pantropical Hoshihananomia Kônô, 1935 (39 species) and Calycina Blair, 1922 (11 species), and the Old World Glipidiomorpha Fransiscolo, 1952 (17 species). About 265 species of Mordellidae occur in Europe while 200 have been recorded from the Nearctic region.

Ecology

Adults occur in a wide range of habitats but in general many will be found on wooded margins and clearings, wooded parkland and gardens and along hedgerows bordering agricultural land. Many species e.g. of Mordella, Mordellochroa and Mordellistena, frequent flowers, and in such situations may occur in numbers and are easily sampled; they may be tubed or the flowerheads may be shaken into a net, but many other species e.g. of Tomoxia and Variimorda, spend much of their time on tree trunks or logs where they run very rapidly and take flight at the slightest disturbance, this behaviour coupled with their cryptic and metallic appearance, make them very difficult to sample. Beating flowers, especially umbels, and foliage generally will occasionally produce specimens. When netted or on the beating tray they will either remain curled-up and motionless for a while or they will instantly begin to run, spin and tumble or somersault over and over, hence their common name, making them very difficult to observe, this behaviour is also seen in some Melandryidae (Orchesia Latreille, 1807) and Scraptiidae (Anaspis Geoffroy, 1762) but is much less rigorous. This behaviour comprises a series of very rapid jumps and spins produced by pushing down and laterally with the large and adapted hind legs. Most specimens will need to be taken for examination as identification can be very difficult. For a long time some species were thought to prey on other insects but there is no convincing evidence that either larvae or adults are predatory; adults are known to feed on pollen and possibly other flower parts, and some species are rarely found away from flowers, those worth searching include umbels generally but in particular Heracleum and Daucus spp. and Achillea millefolium and Crataegus blossom. Larvae have been recorded feeding in fungi, galls, decaying wood and vascular tissue in the stems of a wide range of herbaceous plants and shrubs. In general there seems to be no association between the flowers chosen by adults and the larval hosts, and no species is known to be monophagous or even oligophagous, although some plant species do seem particularly prone to attack e.g. commercial sunflower crops in the United States are often attacked by species of Mordellistena; adults feed on the pollen and females insert their eggs into the stems just under the petioles, early planted crops are most affected and as many as 40 larvae may infest a single plant, each in a separate part of the stem and each feeding on vascular tissues rather than in the pith. Notwithstanding this example, Mordellids are not considered to be of any economic importance. More generally larvae have been recorded developing in the stems of a range of grasses, legumes and herbaceous plants of a wide range of families, the most popular include Asteraceae, Labiatae, Poaceae, Acanthaceae and Fabaceae. A few species of Mordellistena have been reported as leaf-miners of orchids. Adults are usually active in warm weather and most have a short season, generally in late spring or early summer, and they often occur in flight interception and Malaise traps, and some species in tropical areas are regularly recorded at light.

Description

All species are very distinctive and unlikely to be confused with those of any other family; many species of the Scraptiidae are superficially similar but lack the head development and abdominal style. Size varies from 1.5-15mm but most are below 8mm. Colour varies widely, most are rather drab black to brown or testaceous but they are often bicoloured with the forebody and elytra contrasting e.g. in Mordellochroa milleri (Emery, 1876), and many are strikingly patterned e.g. Yakuhhananomia bidenta (Say, 1824), Tomoxia lineella LeConte, 1862 or (especially) the Australian Hashihananomia leucostica (Germar, 1848), or metallic. Most are at least to some extent pubescent and many densely so, this is generally white or grey, fine and recumbent though sometimes scale-like and forming a pattern. The head is large, strongly deflexed and transverse, in many species composed largely of the massive eyes, triangular in frontal view and either continuous in outline with the pronotum or wider than the anterior margin of the pronotum, strongly constricted behind the eyes and attached by a narrow neck. Vertex and frons usually smoothly convex and finely to densely and rugosely punctured. Palps generally small and hidden; labial palps 3-segmented with the terminal segment variously expanded to securiform. Clypeus small but distinct, labrum produced and prominent, generally hiding the short and curved mandibles, mandibles sharply pointed or bifid. Antennae 11-segmented, usually short and filiform but sometimes serrate or clavate, inserted laterally in front of the eyes, Ctenidiinae is unusual in having pectinate antennae. Eyes large and occupying most of the lateral margin of the head, evenly convex and round to oval, sometimes angles and appearing almost square, anterior margin sometimes emarginate, facets fine to coarse. Temples absent or very short and strongly constricted to a narrow neck. Pronotum proportionally small, narrowed from distinct and often acute posterior angles to a rounded anterior margin, as wide as or wider than the elytral base, posterior margin sinuate, lateral margins sometimes narrowly explanate towards the base. Surface smooth, variously punctured and lacking larger structure. Prosternum very short in front of confluent and rounded coxal cavities which are open posteriorly. Mesosternum short and widely transverse, carinate and produced posteriorly, mesocoxal cavities moderately separated. Metasternum large, convex and smooth. Scutellum usually distinct although sometimes partly hidden beneath a backwardly produced median part of the posterior pronotal margin; triangular to semicircular or quadrate and bifid. Elytra narrowed from evenly convex and not-prominent shoulders, often near-parallel in the basal third, generally narrow although broad in some e.g. Mordella spp., and with the apices separately rounded or sometimes almost truncate. Surface punctured and/or rugose, generally lacking striae although many have a partly or nearly complete sutural stria, epipleura not strongly developed, often only evident towards the base. Abdomen with 5 or 6 visible sternites, all distinctly articulated, pygidium generally long and pointed, forming a distinct style which is characteristic of the family. Most species have well-developed wings and can fly, and many have very powerful and rapid flight. Front and middle legs long and slender, hind-legs very robust. Front legs without trocantins. Procoxae large and conical, mesocoxae small and narrowly separated, metacoxae transverse, flat and very large; in most species expanded, and usually contiguous. Metafemora enlarged and flattened, metatibiae slender and flat, often dilated apically, with large apical spurs, metatibiae and tarsi often with oblique or horizontal ridges bearing combs of stiff setae. Tarsi 5-5-4; tarsomeres slender and flattened to cylindrical, without, or with only weakly lobed segments. Claws usually small and gently curved, simple to bifid or pectinate. When disturbed many adults adopt a typical curved, almost shrimp-like posture with the head held close to the anterior margin of the prothorax.

Larvae

Mordellidae larvae are elongate and slender to broadly cylindrical, weakly sclerotized and either glabrous with scattered setae or densely pubescent but for the mouthparts and the apex of the ninth abdominal segment. They range from 5-15mm but most are less than 10mm when fully grown. Head hypognathous, without epicranial sutures and with very short, 2-segmented antennae. Labrum and clypeus distinct though very small, mandibles short and stout to conical, and sometimes with a distinct molar area. Maxillary palps 3-segmented, labial palps tiny and 2-segmented. Prothorax often dilated, sometimes produced over the head, meso- and metathorax smaller and of similar size. Abdomen 10-segmented although appearing 9-segmented from above, each with paired annular spiracles and in some the basal segments have dorsal folds or wart-like tubercles, the ninth segment has a single spine or a pair of short urogomphi, and the terminal segment is tiny and often visible only from beneath.

Tomoxia bucephala Costa, A., 1853 larvae

http://data.nhm.ac.uk/dataset/collection-specimens

UK Species

Tomoxia bucephala Costa, A, 1853 is a very local insect of undisturbed woodland in southeast England. Variimorda villosa (Schrank, 1781) is widespread though very local in woodlands across the south of England and Wales. Of our 2 species of Mordella Linnaeus, 1758, M. holomelaena Apfelbeck, 1914 is widespread though very local in the southeast and the Severn estuary, and there is a record from the Mersey estuary, while M. leucapsis Küster, 1849 is very rare with only a couple of near-coastal records in the south. Mordellochroa abdominalis (Fabricius, 1775) is our most common species, occurring throughout southern England and Wales on flowers in a range of situations. Most of our 12 listed species of Mordellistena Costa, A., 1854 are very local or rare insects of the southeast and one, M. secreta Horák, 1983 is only doubtfully British. At least some species should be expected from diligent sampling; M. pumila (Gyllenhal, 1810) is the most widespread and is sometimes common, and M. variegata (Fabricius, 1798), M. humeralis (Linnaeus, 1758) and M. neuwaldeggiana (Panzer, 1796) should all be expected from flowers in warm weather.