Altica lythri Aubé |
(a leaf or flea beetle)
Order: Coleoptera – beetles
British distribution: Widespread in England and Wales, rarer in the north, rare in Scotland, rare or under-recorded in Ireland; mapped in Cox (2007).
World distribution: Widespread in Europe, extending into Asia and North Africa.
|Altica lythri (as judged on external characters), Wicken Fen, Cambridgeshire, April 2005.|
The family Chrysomelidae is a very large family of plant-eating beetles, many of which are brightly coloured and often with metallic reflections, and some of which are pest species. It includes the "flea beetles" (subfamily Galerucinae, tribe Alticini) and what are most often termed the "leaf beetles" (subfamily Chrysomelinae). Classification follows Cox (2005).
Altica lythri belongs to the Alticini and is technically a flea beetle, and it does indeed jump, albeit with a certain amount of prodding and not to great distance. However, it doesn't have the shape, such greatly enlarged rear femora, or jumping ability, of such genera as Psylloides, Phyllotreta and Longitarsus. With a length of 4.5 to 5.5 mm (Joy, 1932), it is also larger than most 'true' flea beetles and in general appearance is much like the leaf beetles of the Chrysomelinae. Consequently, it is referred to as both a leaf beetle and a flea beetle in literature.
The genus Altica is recognised, in part, by the transverse, depressed line running across the thorax (visible in the photographs above). Seven British species are recognised by Cox (2008) and all except the recently detected A. carinthiaca are keyed in Joy (1932), though under the generic name of "Haltica", and some under names now regarded as synonyms. The genus is not, however, easy, and there is a lack of reliable external characters (see, e.g., Cox, 1991).
A. lythri is generally recognisable by its slightly larger size, maybe brighter blue colour, and by the shape of the elytra, which are somewhat widened towards the posterior.
Useful comparative photographs of all of our species, plus many other non-British species of this large genus, are provided by Borowiec (2004-10), an impressive and invaluable web resource. Note, however, that the metallic colours as perceived in daylight appear differently in the artificial-light photographs on Borowiec's site, and that the very fine punctae of the elytron surfaces are clearer in his photographs than they are under field conditions.
A. lythri feeds openly on leaves of marsh plants, as both larva and adult. Philp (1991) and Bullock (1992) list it as occurring on Epilobium hirsutum (Great Willowherb) and on Lythrum salicaria (Purple Loosestrife). It should be noted that the very similar species, Altica palustris, is also listed for these hosts, and that the polyphagous species, A. oleracea, is listed for Epilobium species.
The beetles shown in the photographs were among a number concentrated in a damp hollow in a drove in Wicken Fen, Cambridgeshire. The sparse vegetation indeed included some much-eaten young shoots of E. hirsutum, from which the beetles appeared to be dispersing.
|• ||Borowiec, L., (2004-10). Chrysomelidae. The leaf beetles of Europe and the Mediterranean subregion (checklist and iconography), http://culex.biol.uni.wroc.pl/cassidae/European%20Chrysomelidae/index.htm.|
|• ||Bullock, J.A., (1992). Host plants of British beetles: a list of recorded associations, Amateur Entomologists' Society, Feltham.|
|• ||Cox, M.L., (1991). Chrysomelidae, in Cooter, J., (ed.), A coleopterist's handbook, ed. 3, Amateur Entomologists' Society, Feltham, pp. 156-170.|
|• ||Cox, M.L., (2007). Atlas of the seed and leaf beetles of Britain and Ireland, Pisces Publications, Newbury.|
|• ||Cox, M.L., (2008). Family Chrysomelidae, in Duff, A.G. (ed.), Checklist of beetles of the British Isles, 2008 edition, http://www.coleopterist.org.uk/checklist2008%20A5.pdf.|
|• ||Joy, N.H., (1932). A practical handbook of British beetles, 2 vols., H., F.& G. Witherby, London.|
|• ||Philp, E.G, (1991). Vascular plants and the beetles associated with them, in Cooter, J., (ed.), A coleopterist's handbook, ed. 3, Amateur Entomologists' Society, Feltham, pp. 183-198.|
© A.J. Silverside|
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