DERODONTIDAE LeConte, 1861

Tooth-Necked Fungus Beetles

This recent introduction is now widespread and can be found by beating conifer foliage, especially smaller pine trees in open situations. 

POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

Laricobius Rosenhauer, 1846 

L. erichsonii Rosenhauer, 1846

1.5-2.6mm

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Introduction

A small family of four genera and more than forty species distributed throughout temperate regions in both the northern and southern hemispheres. The most up to date list (Hava, J., 2006) includes the following:

  • DERODONTINAE

    • Derodontus, 11 species.

  • LARICOBINAE

    • Laricobius, 23 species.

    • Nothoderodontus, 6 species.

  • PELTASTICINAE

    • Peltastica, 2 species.

With the exception of Laricobius they are fungivores, feeding on various moulds, slime moulds, fermenting material and the fruiting bodies of larger species. All members of the genus Laricobius feed on adelgids, small insects similar to aphids. For this reason several have been used in biological pest controls e.g. L. nigrinus has been released into conifer forests in the United States to help control Adelges tsugae (The hemlock woolly adelgid, native to North America). L. osakensis, from Japan, has also been trialled in the U.S. for the same reason. L. erichsonii was introduced into the U.S. in 1962 and is now established there.

Laricobius erichsonii Rosenhauer, 1846

Laricobius erichsonii is now widespread in northern Europe; north Germany, Holland, Denmark and Scandinavia. It is thought to have originated in the Alps and Carpathian Mountains and spread due to the extensive introduction of conifers to new areas during the twentieth century. It was first recorded in the U.K. in Suffolk in 1971 on fir trees and by 1982 records were widespread in the county. In 1972 it was introduced into Kent as a biological control of adelgids on fir trees but the colonies are thought to have died out. The colonies now occurring in Kent are thought to be from natural dispersal from the continent. Its present distribution, based on NBN records, includes Kent, East Anglia, Lincolnshire, and Gloucester through to north Wales and the Lake District. There are a few records from Scotland north to Inverness.

Adult L. erichsonii predate adult adelgids, mostly Adelges picaea (Ratzeburg) but also others, and may also consume the eggs. Gut contents also include fungal hyphae and spores. Smaller Laricobius larvae consume the eggs while later stages predate the adults as well. Adults occur on a range of conifers but mostly Scots Pine and may be swept from vegetation beneath the branches. Overwintered adults appear from April, increase in numbers through May, and are present until July. Locally we have recorded them from young pine (around 1m.) in Whippendel Woods (4/4/2009) and from a larger, isolated tree (around 4m.) on Bricketwood Common (5/5/2012 and 21/6/2015).

Although small, our single species of Derodontidae is distinctive in appearance and with experience will be instantly recognized in the field. The combination of the antennal and tarsal structure and the site of the ocelli will ensure certain identification.

1.5-2.6mm. Black above and below with elytra to varying extents red; at least the base, suture and side margins are usually dark. Antennae, tibiae and tarsi orange. Upperside with erect, pale pubescence.  Head constricted on front of and behind strongly protruding eyes. Surface strongly pitted, between these smooth and very finely punctured. Each side with an ocellus close to the inner margin near the rear of each eye. These may be difficult to appreciate but often appear paler against the surrounding black cuticle. Antennae eleven segmented, segments nine to eleven forming a loose club. Pronotun with very large as well as much finer puncturation. Broadest at middle, sides bordered and fringed with fine pubescence, narrowed towards base and apex. Front and hind angles sharp and protruding. Each elytron with ten strongly punctured striae, towards the apex this puncturation becomes confused. Tibiae weakly angled on outer side, without teeth or terminal spines. Tarsi five segmented but appear to have four as the fourth is very small. Basal three segments strongly lobed below, fifth long and curved. Claws smooth.

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