Diagnostics of bark beetles of the genus Pityokteines Fuchs important in forestry

Abstract

The paper deals with problems of determination of imagoes (mainly females) in bark beetles of the genus Pityokteines Fuchs. P. curvidens (Germ.) is on average only slightly longer than P. spinidens (Reitt.) and distinctly longer than P. vorontzowi (Jak.). Males are (without lower hooked teeth) equally long as females. The shield of P. curvidens is on average 8% (P. spinidens 12% and P. vorontzowi 13%) longer than wider. Males of P. curvidens have wing cases at shoulders equally wide as their shield, females on average 3.3% wider than their shield. Males of P. spinidens have wing cases on average 1.0% narrower (females 2.1% wider) than their shield. Males of P. vorontzowi have wing cases on average 1.3% narrower than their shield, females have wing cases equally wide as their shield. The longest tail-like hair of the shield front edge (about 0.38 mm) occurs in females of P. spinidens, much more shorter (about 0.26 mm) in P. curvidens and shortest (about 0.23 mm) in P. vorontzowi. In females of P. curvidens, the hair of forehead as against the hair of shield is shorter on average by 8.3, in P. spinidens by 5:6 and in P. vorontzowi by 9.5%. Based on the length of the shield hair it is possible to distinguish reliably females of P. spinidens and according to short (0.12 mm) bristles on the rear of wing cases females of P. vorontzowi. A longitudinal central keel occurs on the forehead of 80% males of all three species and 72% females of P. vorontzowi. A figure defined by the teeth of the 2nd and the 5th pair in females of P. curvidens on the rear of wing cases is an isosceles trapezoid that approaches (or is almost equal) to a rectangle. In P. spinidens, it is quite a well-marked (in P. vorontzowi well-marked) trapezoid. It has been found that the shape and size of these figures are the main characteristics for species determination of females of the genus Pityokteines.