Stilbus testaceus (Panzer, 1796)
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
STILBUS Seidlitz, 1872
This generally common and often abundant species occurs throughout Europe north to Southern Scandinavia and east to Greece, Ukraine and Asia, and there are also records further south, from tropical Africa. In the U.K. it is common across Southern England, becoming more scattered in the West Country and north to the Humber, and there are occasional records further afield to Southern Scotland and the Isle of Wight. Adults are active from February to October, depending the season, and also appear occasionally in grass-tussock samples and flood refuse in the winter. They are generally common in dry grassland in a wide range of situations, e.g. meadows, parkland and gardens, and also on sedges, reeds and other waterside vegetation. Sweeping in suitable situations may produce them in abundance. During hot weather they may be found in various yellow flowers along with other small species e.g. Meligethes or Brachypterus, although they readily descend into the base of the flower and may need to be searched for. They fly well and may appear at u.v. light in numbers. Little seems to be known of their biology.
With a little experience species of the phalacridae become obvious among the many other small beetles that regularly occur in the sweep net; species of Stilbus Seidlitz, 1872 are oblong-oval, convex and bicoloured, features shared with some members of the genus Olibrus Erichson, 1845, and so they will need to be taken for examination under the microscope and, often, dissection, in order to obtain a certain identification.
1.8-2.3mm. Convex and broadly oval with the underside flat; dorsal surface dark or light brown with the apical quarter or so pale. Appendages pale. Dorsal surface with very fine punctation, visible at X50. Head transverse and evenly rounded, the eyes continuous with the outline. The anterior and posterior margins of the eyes are weakly sinuate. Antennae inserted under the anterior margin of the head; the 2 basal segments are large, 3-8 elongate becoming shorter towards the apex, and 9-11 form a compact club. The terminal antennomere is evenly rounded laterally. The terminal segment of the maxillary palpi is curved along the inside and straight externally. Pronotum broadest at the sharp, perpendicular hind angles and evenly curved to the weakly protruding front angles (side view). Scutellum small and equilateral. Elytra with a single sutural stria which is wider and deeper towards the apex, the surface has several longitudinal rows of very fine punctures (X50) and some obscure, shallow impressions. A surface microsculpture consisting of transverse wavy lines becomes visible at X70 and is easiest observed on the disc. The lateral margins of the pronotum and the elytra are finely bordered. Legs short, the femora usually not visible from above. All tibiae broad, weakly sinuate and with small terminal spurs. Tarsi 5-5-5, third segment bilobed. Claws smooth and toothed at the base.
Stilbus testaceus 1