On 1st April 2003, Stuart Gant rang me to say that he had found a longhorn beetle on a wine box in the warehouse at Morrison’s supermarket at Sproughton, near Ipswich (TM1345). I collected the beetle from him the next day and back home quickly saw that it was a Xylotrechus species. This non-British genus is characterised within the Cerambycidae by having the side margins of the forehead bordered by a keel-like ridge towards the eyes and antennal bases as well as, in some species including this one, a longitudinal keel in the centre of the forehead. Both of these characteristics are shown well in the accompanying photos as are the excised eyes which are a feature of many longhorn beetles. Using Harde (1966) and Bense(1995) the beetle keyed out readily to X. rusticus L. one of six species of the genus found in Middle Europe. X. rusticus varies in size between 9 and 20 mm (the Sproughton beetle was 13 mm)and is one of the most widely distributed but, like all the species, it is usually rare with many captures of the beetle being based on old records.
It breeds in the solid wood of dead sun-exposed or fallen trunks of a variety of broadleaf trees but chiefly Populus, Salix and Betula species. Xylotrechusis closely related to Clytus, the genus to which our very common and well-known Wasp Beetle Clytus arietis L. belongs. Beetles of both these genera ( unlike those of Trachyderes, a photograph of one of which was featured in issue 54 of White Admiral ) do not have the long antennae which have given the Cerambycidae their popular name of longhorn beetles. The origins of this specimen are uncertain and no evidence of wood in which it might have developed was found in the warehouse. Most longhorn beetles overwinter as adults within the pupal cell, having emerged but remained quiescent there since the previous autumn. If however, the wood containing these beetles is brought from outside into warmer conditions e.g. inside a warehouse, the rise in temperature often prompts the beetle to chew its way out of the wood from its pupal chamber somewhat earlier. The rather early date indicates, therefore, that this specimen had probably not emerged outside as adults of this species do not normally appear in the wild until May. Any members finding possible beetle importations such as this, are urged to send them to me as I intend to include these records in an appendix to the new “Coleoptera” of the county.
I thank Stuart Gant for the gift of the beetle and Adrian Chalkley for his excellent photographs.
Bense, U. (1995).Longhorn Beetles. Illustrated key to the Cerambycidae and Vesperidae of Europe. Weikersheim. Margraf Verlag. .Harde, K. W. (1966). Family Cerambycidae in Die Kafer Mitteleuropas Band 9. Cerambycidae and Chrysomelidae. Krefeld. Goecke & Evers.
David R. Nash
email dr.nash@btinternet.com
© 2003 Suffolk Naturalists' Society