Galerucella calmariensis (Linnaeus, 1767)
Generally common throughout Europe from the Mediterranean north to the UK, Denmark and southern Fennoscandia, also widespread across North Africa and Asia Minor and extending through Russia and Mongolia to China and Japan. Introduced into many sites across the United States and Canada from 1992 as a biocontrol agent for Purple Loosestrife (Lythrum salicaria L.), it is now widely established and spreading. The species is locally common throughout England and Wales, though less so in the north east, widespread but scattered in Ireland and there is an old record from Scotland. Typical habitats are wetland margins, marshes and bogs, peatland and coastal grassland but they sometimes occur in numbers where the host is common in drier habitats such as waste ground and parkland. Adults are present year-round, they overwinter in stems or among litter etc. and are active from April until October, peaking in abundance during June. The species is monophagous on Purple loosestrife, in Europe it has also been recorded from European Wand Loosestrife (L. virgatum L.) although it is not known whether this is a larvae host. Overwintered adults feed on the tips of fresh foliage before mating and females oviposit during May and June. Eggs are laid on the underside of leaves or on stems or leaf axils in small groups of two to ten, this continues for about two months and each female may produce up to 400 eggs over this time. Larvae feed externally, initially on tender leaves and buds but as they grow they will attack any part of the plant, producing large translucent blotches and often causing extensive defoliation during the summer, they develop rapidly, passing through three instars and then falling to the ground to pupate in the soil. The cycle from egg to adult takes about six weeks and new-generation adults appear continuously from late June until September. Overwintered adults persist into the summer and they may occur for a while alongside the new-generation adults, their oviposition periods overlapping, but those emerging later in the summer will not mature sexually until they have overwintered. The species is univoltine in the UK but on the continent there may be several generations each year. Adults may be sampled by sweeping or beating host foliage; they usually occur in numbers and often disperse by flight, seeking out fresh host material, especially on warm days in spring and early summer.
Galerucella calmariensis 1
Galerucella calmariensis 2
Galerucella calmariensis 3
3.9-4.9 mm. Body finely pubescent, pale brown with vertex, pronotal disc, scutellum and a broad longitudinal stripe on each elytron black, antennae pale at the base, becoming darker to the apex, legs pale brown. Head much narrower than the pronotum, finely punctured between large convex eyes and with the antennae inserted anteriorly beyond the front margin of the eyes. Pronotum transverse, broadest near the middle and narrowed to rounded posterior and a rounded apical margin, disc and basal margin matt, contrasting with the shiny apical margin and with scattered large punctures towards the margins. Elytra elongate (about 4.5X longer than the pronotum), parallel-sided or slightly dilated from rounded shoulders to a continuous apical margin and with the explanate margin clearly visible throughout from above and becoming broader around the apex, surface randomly and moderately strongly punctured. Apical abdominal sternite in males with a deep notch which extends beyond the middle, in females with a shallow notch which does not reach the middle. Males with short spurs to the middle and hind tibiae. Typical specimens are easily recognized in the field, especially when swept from the host plant; the longitudinal dark line along the centre of the pronotum and the long elytral stripes are distinctive. G. pusilla (Duftschmid, 1825), which also occurs on the host, can be similar but the pronotum has at most a small and indistinct median spot and the elytra are extensively pale, being darker only about the shoulders. Here the males have a single spur on the middle tibiae and the hind tibiae are unarmed, and females have a much shallower notch to the apical abdominal sternite. Sometimes both species occur together, in which case the difference in colour soon becomes obvious.