Clytus arietis (Linnaeus, 1758)

Wasp Beetle

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POLYPHAGA Emery, 1886

CHRYSOMELOIDEA Latreille, 1802

CERAMBYCIDAE Latreille, 1802

CERAMBYCINAE Latreille, 1802

CLYTINI Mulsant, 1839

CLYTUS Laicharting, 1784

This is a widespread species occurring throughout the Palaearctic from Spain to Greece and the Mediterranean islands.  Further north it occurs throughout Belgium and southern Scandinavia. The distribution extends south through Asia Minor to Syria and northern Iran. Further east through the Caucasus, Kazakhstan, and across south, central and eastern Russia. This is one of the most common European Longhorns. We have so far been unable to find any records from Ireland or the Americas.  In the U.K. it occurs commonly throughout England and Wales including the Isle of Wight, Anglesey and Man. There are only a few records scattered across Scotland north to Inverness but not including the islands. Locally it is usually abundant although we have experienced years of particular abundance as well as a virtual absence. They occur in wooded habitats, generally around fallen branches and logs, but the adults fly readily and may be seen visiting flowers far from any obviously suitable habitat. They visit urban gardens and are sometimes seen in the town centre. Umbels (Apiacaea) and dog rose are among the most frequently visited.  Adults feed on pollen and occasionally small insects, this may be particularly so for the female to provide protein for egg production. Adults may appear as early as March, depending on the season, and arte active until July or August. They mimic wasps both in their appearance and their rapid, jerky movements, and they are said to produce a buzzing sound when threatened although we have so far been unable to elicit this response.

The usual hosts include a wide range of broadleaf species including Acer, Betula, Castanea, Crataegus, Fagus, Pyrus, Tilia, Salix and Ulmus. They have also been recorded developing in Juniperus and Picea abies. Eggs are laid in crevices in the bark of recently fallen or dead trees, fallen branches of posts etc. The larvae initially live under the bark but when about half grown they tunnel into the xylem. When fully grown they construct a pupal cell, parallel to the wood grain, around 3-5cm long at the end of the tunnel. Pupation occurs either during September or October or in the spring of the following year. The entire life cycle generally takes two years but adults have been known to emerge from furniture after several years.

Once familiar this very distinctive longhorn is unlikely to be confused with any other; variation in the markings is narrow and colour varieties are very rare. A variety lacking the yellow V shaped elytral mark (var. medioniger Allen) is described by Allen (1959).  See www.cerambyx.uochb.cz. Until a familiarity with Clytus is gained, the very rare Plagionotus may cause confusion.

9-13mm. Antennae dark, segments 2-4 orange, 3rd longer than 4th. Longer in the male; reaching back toward the middle of the elytra, in the female just over the humeral angles. Apical segment of labial palpi dilated.  Head narrower than pronotum; black with yellow scales beside eyes. Eyes with tiny facets, and strongly excised around antennal tubercles. Temples parallel. Thorax quadrate and lacking lateral borders, spines or tubercles. Front and hind margins narrowly yellow although this is sometimes interrupted posteriorly. Head, thorax and basal half of elytra with outstanding yellow pubescence. Elytra black or lighter apically, marked yellow as shown.  Apices smoothly rounded. Last abdominal tergite with dense yellow scales and often protruding. Legs orange with femora variously darker.  Pubescent throughout.  Mid and hind femora clavate and all femora lacking spines.  All tibiae with an apical spur on the inner side.

Similar Species
Plagionotus arcuatus
  • Generally larger (8-20mm)
  • Antennae entirely pale.
  • Basal transverse elytral mark angled.
  • Occassional adventive specimens recorded, otherwise presumably extinct in the UK.

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