Donacia clavipes Fabricius, 1792
This is the largest UK member of the genus and easily identified by the metallic green, coppery or bronze body and almost entirely pale appendages. D. clavipes is a widespread Palaearctic species occurring from Portugal east through Asia Minor, Siberia and China and north to Scandinavia and the UK. Here it is sporadic and locally common throughout the mainland and scarce in northern and western Ireland. Adults occur on the host, Phragmites australis (common reed), in most still and slow-moving water environments and will usually be found in numbers among the foliage or on the flowers of various plants growing adjacent to reed beds, they feed on young shoots which then develop characteristic irregular elongate holes as they grow. They are active from April to August and mating pairs may be observed in May and June, oviposition occurs in the spring when eggs are laid on the inner surface of lower leaves or low down on the stems. Larvae develop in roots and rhizomes through the spring and summer and in the UK have been observed fully-grown from late June. Pupation occurs in a silken cocoon within the rhizome from August, many may occur together, and adults eclose in late summer and autumn but remain in situ until the following March or April when they may be observed within leaf axils near the water surface.
7-12mm, characteristically large, parallel-sided and vividly metallic with substantially pale appendages, including the tarsi, this species should readily be identified in the field; the presence of large reed-beetles among the host foliage is always worth investigating.