Xyloctonus Eichhoff, 1872

Jordal, Bjarte H., 2024, Integrated taxonomy, biology and biogeography of the Afrotropical genus Xyloctonus (Coleoptera, Curculionidae, Scolytinae), Deutsche Entomologische Zeitschrift 71 (1), pp. 67-84 : 67

Xyloctonus Eichhoff, 1872

Type species.

Xyloctonus scolytoides Eichhoff, 1872 (by monotypy).

Diagnosis.

Eyes divided, except broadly emarginated in X. maculatus and X. genieri sp. nov. Antennal scapus longer than the 6-segmented funiculus; club flat, outline round, with three, or more rarely two, strongly procurved sutures marked by dense white or golden setae (Figs 22 , 40 ). Pronotum spherical in both lateral and frontal view, lateral margins carinate; anterior half asperate, with either two or four raised teeth along anterior margin. Scutellar shield (scutellum) slightly detached from elytra; interstriae carinate (only declivity in X. aethiops ), interstrial carinae either reaching posterior margin or more often disrupted by a curved interstriae 9 that reaches elytral suture near apex; declivity short and gently sloping (steep and longer in X. maculatus ). Metanepisternum, metaventrite and first ventrite usually with split setae, trifid or occasionally plumose setae often present near mesoventrite. Ventrites 3-5 usually steeply rising to meet elytra. Procoxae contiguous; protibiae with deep furrow of anterior face to receive tarsi; other tibiae with distinct, but shallower furrow on its posterior face. Proventriculus with posterior plate strongly reduced, anterior plate with partially open and indistinct median suture, plate covered by simple obtuse tubercles. Male genitalia with large complex intromittent organ (basal sclerites), apophyses (penis apodemes) as long as penis body; tegmen open dorsally, ventrally with a large scoop-shaped manubrium; spiculum gastrale as simple thin curved rod.

Differential diagnosis.

This genus differs from Scolytomimus by the distinct procurved sutures in the antennal club and by the irregular impression around the scutellar shield. It is further distinguished from Cryphalomimus and Ctonoxylon by the 6-segmented antennal funicle, a rather short, oblique elytral declivity and the symmetrically procurved sutures in the antennal club.

The Xyloctonus emarginatus group

Two species are included in this group, defined by having all interstriae reaching the apical margin of the elytra (Fig. 5 ). One of the taxon names used in the past was ' Xyloctonus emarginatus ', now a synonym of Xyloctonus scolytoides , describing this condition (see Xyloctonus bimarginatus group below).

Figures

Figures 16 - 24. Dorsal, lateral and front view of holotype of X. opacus (16, 19, 22); paratype of X. punctipennis (17, 20, 23); X. biseriatus (18, 21, 24).

Figures 34 - 42. Dorsal, lateral and front view of X. bimarginatus (34, 37, 40); X. maculatus (35, 38, 41); X. genieri, holotype (36, 39, 42).

Figures 1 - 5. Posterior view of elytral declivity in 1. Xyloctonus quadridens; 2. X. maculatus; 3. X. subcostatus (paratype of X. striatus); 4. X. pubifer; 5. X. scolytoides (paralectotype of X. latus). Black arrows points at the shallow furrow on the posterior side of the metatibiae, similar to mesotibiae. White arrow points to the impression of the metaventrite which receives the metafemur. Yellow arrows point at elytral interstriae 9, which in Figs 1 - 4 runs to the elytral sutures and blocks interstriae 1 - 8 from reaching elytral apex; in X. scolytoides (Fig. 5) all interstriae reach the posterior margin of the elytra.