Zabrus tenebrioides (Goeze, 1777)
This is a common and often abundant species throughout Europe from Spain to Western Russia, Ukraine and Kazakhstan, extending north to Denmark and Southern Scandinavia and south to North Africa and Asia Minor. In the U.K. it is a very local species of central and southern England with many records from coastal areas of Dorset, Hampshire and Sussex, and there is a single record from South Wales. The typical habitat, or at least the habitat where it might attract attention, is agricultural land used to grow wheat, barley and, occasionally, oats. They are rarely little more than a nuisance but on the continent, at least up to the middle of the 20th century when agricultural practices and the use of treated seeds helped to control the species, it was occasionally a serious crop pest, being responsible for stripping areas of fields down to bare soil. New generation adults appear from early summer and climb stems at night in order to feed upon seeds for a while before dispersing by flight for short distance over crops, they continue feeding nocturnally through the summer although during the warmest periods they burrow down to about 40cm in the soil and remain inactive until the temperature falls later in the summer when they resume feeding once more. They mate from early summer and oviposition begins in June or July, although generally a little later in the U.K.; females deposit small batches of 3-5 eggs in depressions or burrows in soft soil, and each will lay up to 250 eggs. Larvae emerge between 1-3 weeks later and begin feeding nocturnally on leaves, climbing stems to do so, as they grow they burrow down as far as 40cm into the soil and pull in leaves so that they can continue feeding during the day. An indication of the presence of larvae is skeletonised leaves around the bases of stems in discreet feeding areas although when present in numbers these areas are extensive and completely stripped plants are usually present. They continue feeding until the onset of cold weather when they retreat into the burrows to overwinter, occasionally feeding during mild spells, and resume feeding in the spring. Pupation occurs in an underground cocoon in the spring, generally late April to Late May, and adults eclose after 2 or 3 weeks. The adults will damage seed heads from the onset of flowering to when they are fully mature and they are often completely destroyed, the beetles move quickly between plants through the summer and they are long-lived, often overwintering in the soil beneath the host plants.
14-16mm. A large and very convex carabid; oblong-ovate with rounded elytral apices that completely cover the abdomen. Entirely black, often with a weak metallic sheen, with the tibiae, tarsi and antennae variously pale. The entire upper surface is glabrous. The head is proportionally large with convex and vaguely wrinkled vertex and frons, protruding eyes and a single supra-orbital puncture- which is unique among the U.K. Zabrini-the temples are long and broadened towards the base. Mandibles broad and robust; bluntly pointed and smooth along the outer margin i.e. without any setiferous punctures. Apical segment of the maxillary palps cylindrical and much shorter than the very elongate penultimate segment. The antennal colour varies but they are generally darker towards the apex and paler towards the base, the third segment is glabrous and so contrasts against the fourth segment. Pronotum transverse and strongly bordered laterally, almost straight in the basal half and evenly rounded to obscure front angles, the base is weakly foveate and extensively punctured, often with fine transverse wrinkles. The narrow explanate side margin and the area behind the anterior margin are usually finely punctured and the hind angle lacks a sensory seta. The side margin and the base are often pale brown. The elytra are broadest a little behind the middle and each has 8 well-impressed and punctured striae as well as an abbreviated scutellary striole, the eighth striae is regularly impressed to the apex and the epipleura are not crossed. The interstices are convex and lack setiferous punctures, the entire surface is microreticulate, much more strongly so in the female. The base is strongly bordered and evenly convex; without protruding humeri. The legs are robust and relatively short, the tibiae and tarsi generally lighter when compared to the black femora. Meso- and meta-tibiae with rows of strong spines, expanded apically and with two Long and unequal spurs at the apex. Pro-tibiae greatly expanded towards the apex, with a large and broad spur on the inner apical margin and a smaller spur beneath this, the inner margin with a well-developed antennal-cleaning notch. All tarsal segments with short and stiff spines below, the claws smooth and proportionally very narrow. Male pro-tarsal segments strongly dilated.