Cantharidae | UK | Ukbeetles

CANTHARIDAE Imhoff, 1856

Soldier Beetles

These conspicuous beetles occur in a wide range of habitats, with common species such as Rhagonycha fulva being especially abundant in the spring and summer.

POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

2-15mm

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Around the World

This is a cosmopolitan family containing around 6000 species in 150 genera and 5 or 6 subfamilies although various Lampyrid subfamilies e.g. Pterotinae LeConte, 1861 and Ototretadrilinae Crowson, 1972 have sometimes been considered as belonging here. The Cydistinae Paulus, 1972 was originally erected to include the single Palaearctic genus Cydistus (Bourgeois, 1885) which has more generally been included in the Rhagophthalmidae Olivier, 1790. The Cantharinae Imhoff, 1856 is most diverse in the Holarctic and Oriental regions and extends south India, Malaysia, North Africa and Central America; it is the largest subfamily with about 70 genera and more than 3000 species and includes 2 tribes; Cantharini Imhoff, 1856 and the larger Podabrini Gistel, 1856. Silinae Mulsant, 1862 is a large group of about 50 genera and more than 850 species included in 2 tribes; Silini Mulsant, 1862 and the much larger Tytthonyxini Arnett, 1962, although cosmopolitan the group is primarily tropical and only poorly represented in temperate regions. Silini is widespread but notably absent from New Zealand, Tytthonyxini, by far the most diverse group, includes the atypical New World genus Tyttonyx LeConte, 1851 (sometimes placed in the Malthininae) which includes species with abbreviated elytra and serrate or flabellate antennae. The Dysmorphocerinae Brancucci, 1980 includes about 10 genera of mostly southern hemisphere species, in the New World extending north to Arizona, and more generally from southern Africa, New Guinea, Australia and New Zealand. Malthininae Kiesenwetter, 1852 includes 3 tribes and is almost cosmopolitan, being absent from New Zealand and represented in Australia by only a single species of Malthodes Kiesenwetter, 1852 which is probably introduced. Chauliognathinae LeConte, 1861 includes 2 tribes; Chauliognathini LeConte, 1861 occurs throughout the New World and Australasia while Ichthyurini Champion, 1915 is more widespread although absent from Australia and most of Europe. Although there are likely to be changes to the content and placement of various genera etc. it seems that a 5 or 6 subfamily system, with or without the Cydistinae, is stable for the time being. The family has been rather well-defined and stable from its beginning although for much of the nineteenth century it was called the Telephoridae and included within the Malacordermata, a ‘dumping ground’ for various soft-bodied and otherwise ‘awkward’ groups; it was treated by LeConte as a subfamily of the Lampyridae, and the Chauliognathinae was

for a while considered a distinct family. Dysmorphocerinae was erected in 1908 to accommodate some genera not easily placed within the other subfamilies. But despite these changes the group remains rather characteristic and stable.

Ecology

The majority of adult cantharids occur among grassland, herbaceous foliage or in the shrub-layers of open forested areas, wooded pasture and wasteland, most occur in numbers and some can be particularly abundant on agricultural borders, and among hedgerow foliage etc., in arid region they generally occur among or near riparian vegetation and trees. The adults of most species are diurnal and may be swept from suitable foliage in a wide variety of situations, many temperate species have a short season and may occur initially on flowers, especially those of Apiaceae, in large numbers when mating pairs will often be observed. The season for many is middle to late-spring into early July although many will be seen in small numbers into August, and some e.g. the ubiquitous Rhagonycha fulva (Scopoli, 1763) have a later season. Many species become inactive during the warmest part of the day, remaining under leaves until the temperature drops in the late afternoon. Many tropical species are nocturnal and some are abundant in light traps in forested areas. Cantharids generally have a mixed diet of insects, pollen and nectar, all are liquid-feeders both as larvae and adults and a few species are significant predators of aphids in commercial forest areas. The majority are generalist feeders and there do not seem to be many examples of host specificity, one notable example is the ‘goldenrod leatherwing’ Chauliognathus pensylvanicus (DeGeer, 1774), a common Nearctic species which is particularly attracted to Solidago (goldenrod) flowers in the autumn although the adults consume insect larvae and eggs etc. as well as pollen and nectar. It is thought that, in general, any particular adult-host association is determined more by larvae ecology. Most adults are very active, they fly readily and spend much time exposed among vegetation or on flowers, and as a defence mechanism many have evolved aposematic colouration and/or chemical defences; both adults and larvae of many species possess paired thoracic and abdominal glands which secrete chemicals to deter predators. Some species form mimicry complexes with adults of other families e.g. Pyrochroids, Clerids, Melandryids and Lampyrids etc. Several species of fungus are known to attack cantharids, probably with some specificity, e.g. Eryniopsis lampyridarum (Thaxter) and Zoophthora radicans (Brefeld), and infected adults are occasionally seen dead hanging under the surface of leaves, some species of Podabrus Westwood, 1838 and Rhagonycha Eschscholtz, 1830 seem especially prone to infection. The larvae are generally ground-living, among plant-litter or in the soil where the humidity is high; they are primarily predaceous, consuming other insects, eggs and larvae and various other arthropods and molluscs etc. Winter is passed in the larval stage and many are active at this time, even in very low temperatures, on the surface or among litter and debris, they are generally covered with dense hydrofuge pubescence which is probably an adaptation to areas that are prone to winter water logging. The larvae of many are nocturnal and rarely seen at other times; they are generally abundant and will soon turn up in winter tussock and litter extraction samples.

Description

Adult Cantharids may generally be distinguished from those of other families by the following: weakly sclerotized and soft-bodied with the head mostly exposed in front of the pronotum, 11-segmented and usually filiform antennae but in some groups they are pectinate or flabellate, labrum membranous and often obscured by the clypeus. Mesocoxae touching, or nearly so. Tarsi 5-segmented with various segments, but especially the third, lobed. Abdomen with 7 or 8 segments, the tergites with lateral glands. Adults vary widely in size from about 1mm to about 30mm in some tropical species, are mostly elongate and parallel-sided with a large, exposed head and prominent eyes. All are soft-bodied and they vary widely in colouration from entirely black to testaceous and many display warning colours, generally the pronotum is bright red or yellow, contrasting against a dark head and/or elytra but great variation is seen and in some the elytra are patterned. In most the dorsal surface is clothed with short recumbent pubescence; this may be single or double and there may be larger setae. Head prognathous, sometimes angled down (Silis) or, rarely, hypognathous (Ichthyurus), usually with distinct temples which are gradually narrowed towards the base (Cantharis) or rounded (Malthodes) but sometimes abruptly constricted (Podabrus). In some the eyes are dimorphic, being larger in the male. Antennae 11-segmented, insertions on the vertex near the anterior margin of the eyes, insertions widely to moderately separated, rarely touching (Ichthyurus). Anterior margin of clypeus variable; from rounded to emarginate, frontoclypeal suture absent except in Chauliognathini. Mandibles generally elongate and curved, usually smooth although sometimes with an inner tooth or, in Malthodes, serrate. Labial palps 3-segmented, maxillary palps 4-segmented, the terminal segment cylindrical and pointed to widely expanded. Pronotum generally near-quadrate, transverse, e.g. in Silis and Malthodes, or elongate in some Podabrus. Lateral margin variously bordered, generally entire but sometimes incised e.g. Silis, and often explanate, mostly sub-parallel to broadest at the base and narrowed anteriorly, anterior angles rounded to well-defined, the surface variously depressed. Pro-coxal cavities contiguous and very broadly open, the coxae conical and projecting. Meso-coxal cavities contiguous or nearly so and open laterally. Meta-coxae contiguous or narrowly separated, and flat, the lateral margins of the metasternum sinuate. Scutellum exposed, usually well-developed and coloured as the pronotum. Elytra soft, generally parallel-sided or weakly broadened towards the apex, usually covering most of the abdomen and the hind wings, sometimes, rarely, abbreviated. Surface smooth and randomly punctured, sometimes with distinct punctured striae e.g. Malthinus, and sometimes roughly sculptured or rugose, epipleura usually wide at the base and attenuating towards the apex. Abdomen generally with 7 free ventrites in the female and 8 in the male although there are exceptions, apical segment in the male usually modified, sometimes with well-developed accessory structures e.g. in Malthodes. Legs generally long and slender, without large teeth or otherwise modified, the tibiae usually with 2 apical spines. Tarsi 5-segmented with various segments lobed or dilated, claws very variable; often unequal, asymmetrical or with basal lobes on one or both. Hindwings well-developed.

Larvae

The larvae are campodeiform; elongate and convex, in life they are agile and can move fast, most look velvety black or brown/purple, sometimes with red, yellow or white spots, and often with pale legs. Head well-sclerotized and flattened, with an elliptical ocelli on each side, antennae 3-segmented, the penultimate segment truncate or strongly emarginate, frontoclypeal suture absent or only weakly-defined, labrum fused to the clypeus, mandibles curved and sharp with a distinct longitudinal channel. Maxillary palpi 3 or 4 segmented. All thoracic and abdominal segments with paired glandular pores laterally. Legs 5-segmented. Urogomphi absent, in some species with robust apical hooks.

UK Species

The UK Cantharid fauna includes 41 species in 7 genera, 5 tribes and 3 subfamilies. They vary in size from 2 to 15mm and are variable in appearance although in our limited fauna they will soon become familiar and so distinct from superficially similar species e.g. Dasytidae, Drilus and some Tenebrionoidea. They are all soft-bodied, elongate and more-or-less parallel-sided with elytra that almost cover the abdomen. The antennae are long, slender and filiform and are inserted between the eyes on the frons. The anterior margin of the frons completely covers the clypeus. The prosternal process extends back between the coxae and the middle coxae are contiguous. All tarsi have 5 obvious segments, some of which are bilobed. Many are generally common from late spring into early summer and there is a succession of species continuing through to September when Rhagonycha fulva will still be around. They will be found by sweeping long grass and low vegetation or beating shrubs etc. Woodland clearings, hedgerows and margins, where flowers and foliage should be examined, are generally productive in species. Some are associated with particular habitats e.g. Rhagonycha limbata Thomson, C.G., 1864 prefers dry pastures, Rhagonycha lignosa (Muller, O.F., 1764) is arboreal while Silis ruficollis (Fabricius, 1775) and Cantharis pallida Goeze, 1777 prefer open marshy situations. Our only member of the Silinae Mulsant, 1862, Silis ruficollis, is a local insect of Southern England and Wales. It is a distinctive species; 6-7mm and black with the pronotum, tibial bases and mandibles red. The pronotum is coarsely punctured throughout and deeply notched at the posterior angles. Each elytron has 3 obscure raised longitudinal lines. Malthininae Keisenwetter, 1852 includes 4 species of Malthinus Latreille, 1806 which have the mandibles toothed internally, and 12 species of Malthodes Keisenwetter, 1852 in which they are simple. All species are small and have short elytra which partly expose the wings and abdomen. Members of the Cantharinae Imhoff, 1856 have long elytra which cover, or nearly cover, the wings and abdomen. Podabrus alpinus (Paykull, 1798) is very distinctive. Ancistronycha abdominalis (Fabricius, 1798) is a local insect of Wales and Northern England, its metallic black or blue elytra are distinctive. It differs from Cantharis Linnaeus, 1758 (15 species) and Rhagonycha Eschscholtz, 1830 in having all the claws entire. In Cantharis the anterior claw of each pair is toothed and the third meso- and meta-tarsomeres are bilobed. In Rhagonycha the third tarsomere is simple and the claws are divided longitudinally from the apex.

It is thought that all British species have a single generation each year; adults are generally short-lived, laying eggs early in their season. Larvae emerge soon after the eggs are laid and develop through the summer and following winter, with many species of Rhagonycha and Cantharis passing through up to ten instars, and pupating in the soil the following spring/summer.