Sermylassa halensis (Linnaeus, 1767)
The European distribution of this species is mostly restricted to lowlands across central Europe from France to Ukraine although, exceptionally, it occurs up to 1500m in the French Pyrenees and to 2000m in Spain, it is absent from many southern areas and sporadic further north to southern Sweden and the UK, further east it is more widespread, extending through Asia Minor and Russia to Central Siberia. Here it is locally common throughout England and Wales, including Anglesey and the Isle of Wight, and very local and rare in southern Scotland. Adults are active over a long season, from April until November, peaking in August and September, they may be swept from low vegetation wherever the host plants occur, typically wooded margins, heath and moorland, parks, road verges, coastal dunes, river margins and gardens, they fly well and during the warmest months may be attracted to light. Hosts include various Bedstraws, Galium spp. (Rubiaceae), but especially hedge bedstraw, G. mollago L. and, to a lesser extent, heath bedstraw, G. saxatile L., lady’s bedstraw, G. verum L. and cleavers, G. aparine L., they have also been recorded from calamints, Clinopodium spp. (Mentheae). Mating occurs in late spring and continues through the summer, by July gravid females are common and oviposition begins in late July and continues into the autumn, in northern Europe also into the winter; batches of eggs are laid in the soil among host roots and the adults generally die off later in the year although at least some survive to overwinter. Eggs overwinter in the soil and larvae emerge from May until mid-June, they develop rapidly, passing through three instars and becoming fully-grown from mid-June, pupation occurs in a subterranean cell beneath the host and new-generation adults appear from mid-July. Adults feed for about three weeks before mating and ovipositing, they are easily observed as they consume host foliage whereas larvae feed on foliage and stems and may be very difficult to spot. Both larvae and pupae are parasitized by the carabid Lebia chlorocephala Hoffmannsegg, 1803 and adults are known to predate the larvae.
The size, 4.5-7.0mm, coupled with the distinctive colouration should make this species easy to identify. Head and pronotum pale brown, elytra and a variable marking on the vertex metallic green to bluish-green or coppery, rarely bright golden-green, appendages pale to dark brown with the tibial apices and tarsi generally black. Head transverse with large convex eyes and deeply furrowed clypeus, antennae inserted between the lower margins of the eyes, separated by about the length of the basal antennomere. Pronotum transverse and only weakly rounded laterally, anterior angles prominent and rounded, posterior angles rounded but distinct, lateral margin strongly bordered, apical margin finely so and the basal margin simple. Pronotal surface with strongly impressed either side of the disc, these often merging to form a single transverse impression, very finely and sparsely punctured. Scutellum large, triangular and smooth, at most with sparse and very fine punctures. Elytra broadly elongate, with rounded shoulders and a continuously rounded apical margin, dilated to the apical third, much more strongly so in the female, smooth but for a short impression behind the shoulders, punctation strong and dense, for the most part random but with a tendency to from rows, especially in the basal half. Elytral margins explanate to the apex, epipleura wide from the base and narrowing in the apical third. Legs long and robust; femora and tibia smooth, tarsi pseudotetramerous, claws appendiculate. The sexes are usually obvious from the general form of the elytra but can be confirmed by the margin of the apical sternite; in the female it is simply curved while in the male it is sinuate and has a median lobe.