LYCIDAE Laporte, 1836
Net-Winged Beetles
All species are saproxylic, adults are sometimes found on woodland vegetation. The distinctive colour and appearance make this group easily recognizable.
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POLYPHAGA Emery, 1886
ELATEROIDEA Leach, 1815
4
4
5-13mm
Around the World
This is a cosmopolitan though predominantly tropical family of about 4600 species classified among 6 subfamilies although various systems may be found in the literature and the faunas of some regions e.g. the Neotropical, are only poorly known and so the total is likely to be very much higher. The greatest diversity is in humid tropical areas around the world and temperate faunas are generally poor; some 400 species are known from the entire Palaearctic region and most of these are from eastern areas, particularly China and Japan; only 20 species are recorded from the western Palaearctic and of these 12 are European; 9 occur in Central Europe of which 4 extend to the UK. The distribution of many non-tropical species is very restricted, especially in south-eastern Europe and North Africa. They are soft-bodied beetles broadly similar to those of several other families in the Elateroidea series, especially Cantharidae and Lampyridae; in the present family the head is not entirely covered by the pronotum, a character that will distinguish them from lampyrids, and the elytra have 3 or 4 strongly raised longitudinal costae on each, usually with connecting reticulate cells, these costae are lacking in cantharids and while many lampyrids have them they lack the connecting cells. Other distinguishing features include the distinctly separated meso-coxae and long trocanters with off-set or only slightly oblique femoral connections; in lampyrids they are obliquely connected and in cantharids strongly so. Species vary widely in size from 3mm to 80mm and females of many are larger than males, most are brightly coloured and patterned with combinations of black, red and yellow although blue and violet are also common in tropical species. In most species all the developmental stages are known to produce defensive chemical fluids called pyrazines (among others); fatty acid derivatives which give many a distinctive and unpleasant aroma, and many brightly coloured tropical species are mimicked by beetles of other families as well as moths and other insects, they do not have defensive glands but will reflex bleed when handled or alarmed, generally from the base of the elytra, and in feeding tests lycids have been ignored by various spiders and Coccinellids as well as avian predators. Some are known to be involved in complex mimetic relationships e.g. North American species of Calopteron Guérin-Méneville, 1830 and Lycus Fabricius, 1787 have cerambyicid mimics that are known to prey on them.
Description
They are typically elongate and rather flat beetles with a small, hypognathous and usually triangular head, transverse to slightly elongate and usually heavily sculpted pronotum and long, near parallel-sided elytra although in many tropical species these are widely dilated or otherwise modified; in some South African species of the pan-tropical genus Lycus the base is expanded into posteriorly directed processes giving them the common name of ‘Hook-winged Net-winged Beetles’, and in others the apices are produced into broad lobes, sometimes they are sexually dimorphic being normal in the female and variously expanded or widely explanate in males, and in some tropical species they are polymorphic regarding shape and colour. The elytral costae vary widely; they may be faint or almost absent or there may be only one or two present, in some explanate tropical forms the elytra are almost entirely smooth but in temperate species the costae are well developed and so members of the family are obvious. The head is small and only partly hidden by the pronotum, usually without a rostrum but see e.g. species of the Australian genus Porrostoma Guérin-Méneville, 1838, the ‘Long-nosed Lycid Beetles’, dorsally flattened or with various well-defined depressions, small eyes and prominent antennal tubercles, transverse labrum, 4-segmented maxillary palps,3-segmented labial palps and short curved mandibles. The antennae are usually long and stout, gradually thickened towards the apex, serrate or pectinate. Pronotum very variable in shape, often with produced lateral margins or posterior angles, the surface with various carinae enclosing or partly enclosing well-defined cells and often delimiting the margins. Scutellum well developed and usually large, triangular or rectangular. Abdomen usually with 8 free sternites in the male and 7 in the female, in most completely concealed beneath the elytra. Sexual dimorphism is generally poorly developed in temperate species but in warmer areas may be extreme and one group is of particular interest; Platerodrilus Pic, 1921 is a genus of about 25 species occurring in south and Southeast Asian tropical rainforests, females are larviform, reaching 40-80mm in length and distinctive with wide body segments and lateral extensions to the abdomen earning them the common name of Trilobite beetles, while males are of normal lycid appearance and much smaller, 8-10mm. In most lycids both sexes are fully winged and known to fly well.
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Ecology
Most species occur in woodland or wooded areas, adults generally have a short season and are rarely encountered although they may swarm on trunks, fallen timber or herbaceous or scrub vegetation close to their development site, and some may appear on flowers, probably feeding on pollen and nectar. Many oviposit on the bark of dead or injured trees or among leaf litter and many species do so in numbers over a small area. Larvae are generally elongate, flattened and often have lateral projections on the abdominal segments, they develop in decaying wood, usually close to the soil, among litter or in the upper layers of the soil, and a small number of mostly tropical species are known to develop in living trees. Pupation usually occurs in the soil, less often among dead wood; the larvae do not construct cells but usually pupate within the final larval skin, in warmer areas larvae may form large and spectacular congregations prior to pupation, and after emergence the adults may form large local swarms before dispersing. The diet of most is unknown but it is thought that larvae feed on microorganisms or the metabolic products of fungi within the host material, they are variously quoted in the literature as feeding on slime moulds, fungi, fermenting plant juices or that they may be predaceous. Adults are variously quoted as predaceous or as pollen, nectar honeydew or sap feeders and short-lived species may not feed at all.
UK Species
The UK list includes 4 species of Erotinae LeConte, 1881, none of which is common and two of which are very rare indeed. Platycis minutus (Fabricius, 1787), a widespread southern woodland species, is the only one at all likely to be found. Adults are short-lived, seasonal and most easily found on flowers or aggregating on or around dead wood. Our species are very distinct and obvious due to the colouration and elytral sculpture; all are bicoloured red and black, the pronotum and elytra have a series of raised lines enclosing cells, the antennae are filiform or only weakly serrate and the tarsi are 5-segmented with the third and fourth bilobed; the form of the tarsi will further distinguish lycids from superficially similar species e.g. some oedemerids. Sweeping vegetation around likely timber or examining bark or decaying heartwood are the best ways to sample adults although they will occasionally occur among extraction samples of heartwood etc, they generally move slowly and will drop to the ground when disturbed and may play dead for some time in the sweep net and so patience and diligence will be needed. Our species are easily distinguished using the following key.
1.
Anterior pronotal carinae separately connected to the anterior margin.
Anterior pronotal carinae converging to enclose a cell before the anterior margin.
2.
Pronotum and scutellum entirely black, elytra brilliant red, terminal antennomere red.
Pronotum brown with the disc darker, elytra reddish-brown, antennae entirely dark.
3.
Pronotum entirely black. Disc of elytra with 4 longitudinal costae, each separated by a single row of cells. Antennomeres 2 and 3 subequal.
Pronotum extensively red, at least around the raised parts. Elytra with 4 longitudinal costae, each separated by a double row of cells. Antennomere 2 much shorter than 3.