Galerucella lineola (Fabricius, 1781)
Generally common and often abundant, this species occurs across the entire Palaearctic region, from Europe through Russia and Asia Minor to Kazakhstan, Siberia, Mongolia, China and Japan, it is widespread in Algeria and Morocco and is also known from Iran. The European distribution extends from Portugal and Spain to Greece and Ukraine in the south and north to the Arctic Circle; it is yet to be reported from some parts of the Balkan Peninsula and the eastern Baltic region but the distribution is probably continuous throughout. The nominate subspecies occurs throughout while in Italy it is sympatric with ssp. solarii Burlini, 1942. In the UK it is common throughout England and Wales and the north of Ireland, including all the islands, and much more local and scattered further north to the Scottish Highlands and in the south of Ireland where it seems to be mostly coastal or near-coastal. The species is generally confined to lowlands and typical habitats are wetlands and permanently damp grassland e.g. alder and willow carr, floodplains, fens, marshes, and margins of ponds, lakes and rivers etc., but it occurs on a range of broadleaf trees and may also occur in drier areas where the hosts are common; moorland, calcareous grassland, coastal pasture and dune slacks. This is the only UK member of the genus associated with trees, and while adults sometimes occur on various herbaceous plants during spring and early summer, these are not considered to hosts. A wide range of host trees may be found in the literature, including some unlikely species such as False Acacia (Robinia pseudoacacia L.), but the usual hosts include various willows (Salix L.) and alders (Alnus Mill.), while adults often occur on Black Poplar (Populus nigra L.) and Silver Birch (Betula pendula Roth.) Adults occur year-round, they overwinter under bark, in dead umbel (Apiaceae) or willow herb (Epilobium L.) stems or in grass and sedge tussocks and are active over a long season from early spring until the autumn, peaking in abundance during May and June. Adults mate after a period of feeding when they nibble small holes in host foliage, these may become extensive and damage areas of leaves and, at least in Europe, the species is sometimes considered harmful to commercially grown saplings. Oviposition begins in early June and continues until late in July; eggs are laid in small batches on the underside of leaves and larvae emerge after a week or so. Larvae feed on lower epidermis, they pass through three instars and are fully developed within three or four weeks, at which time they fall to the ground and pupate in a subterranean cell. Larvae may be found until late August but new-generation adults appear from July until late in September, overlapping with the overwintered adults which persist into the summer. These new generation adults will not become sexually mature until they have overwintered and fed in the spring and so the two generations are unlikely to breed. Adults fly well and disperse between feeding sites during the spring but they have been found in flight-interception traps through the summer and so might suddenly appear in well-worked sites, they are easily sampled by sweeping or beating host foliage and they usually appear in numbers.
Galerucella lineola 1
Galerucella lineola 2
Galerucella lineola 3
4.0-5.4 mm. Dorsal surface finely pubescent throughout, entirely pale brown to yellowish with a dark spot on the vertex and the pronotal disc and dark scutellum and humeral calli, antennae usually paler at the base (at least ventrally), dark at the apex and with intermediate segments bicoloured, legs pale or with the tibial apex and tarsi darkened. Darker specimens occasionally appear; here the head and pronotum are more extensively darkened and the elytra may be mostly dark with pale margins. Pronotum transverse, broadest about the middle and strongly narrowed to obtuse anterior angles and slightly protruding posterior angles, surface uneven and very finely punctured between sparse larger punctures. Elytra gently curved from rounded shoulders to a continuous apical margin, explanate margin broadest about the middle and narrowed apically, often not, or only very narrowly, reaching the apex, surface without striae, very finely punctured between larger punctures which are about as strong as those on the pronotum. Elytral epipleura narrowed from the base and only just reaching the apex. Legs long and robust with all femora of similar width and tibiae hardly broadened from the base. Male front and middle tibiae with short apical spurs, hind tibiae unarmed. Apical sternite in females with a small notch on the apical margin. Distinguished from our other members of the genus by the finely pubescent pronotum and apically narrowed elytral explanate margins and epipleura.