Anthribus nebulosus Forster

Janicki, Julia & Young, Daniel K., 2017, Nemonychidae and Anthribidae of Wisconsin (Coleoptera: Curculionoidea), Insecta Mundi 2017 (579), pp. 1-36 : 11-12

Anthribus nebulosus Forster

( Fig. 13–14 )

Anthribus nebulosus Forster 1770: 5 .

Antribus variegatus Fourcroy 1785: 136 .

Bruchus clathratus Herbst 1786: 158 .

Bruchus varius ( Fabricius 1787: 42) .

Anthribus capsularis Scriba 1790: 129 .

Brachytarsus nebulosus (Forster) ; Kuster 1859: 457.

Description. Length 1.5–4.6mm. Body oblong. Integument brown to dark brown; beneath vestiture slightly microsculptured and shining. Vestiture consisting of tessellate, dark brown and whitish-grey, hair-like setae, that of antennae and legs darker or paler brown. Head distinctly broader than long, broadest basally thence strongly narrowed apically in rounded lines. Rostrum flattened and broad, narrowed apically; apex truncate, without central prolongation. Antennae 11-segmented, with 3-segmented conspicuous terminal club. Eyes entire, round. Pronotal width about 1.7X length, sinuate basally and with slightly pointed basal projections; lateral carinae reaching middle of pronotum only; surface strongly, densely punctate; basal fovea absent. Scutellum small, round to triangular. Elytral length about 1.6X width, about 2.0X. pronotal length, width slightly over 1.0X pronotal width; shape oblong, parallel-sided; striae distinct; interstriae wider than striae, not punctate apart from microsculpture, interstriae 1–4 with sub-basal bulge, interstria 3 with vestiture raised. Pretarsus with each claw toothed. Pygidium vertical.

Diagnosis. Anthribus nebulosus can be distinguished from other species of Anthribus by the shortened lateral pronotal carinae that are present only along the basal portion of the pronotum. It can be distinguished from other anthribid species by the fused or connate lobes of the 3 rd tarsomeres, rostrum that narrows apically and lacks the apical prolongation in the central 1/3 (in contrast to Trigonorhinus ), and by the tessellate vestiture.

Natural history. Anthribus nebulosus preys on, and is a parasitoid of, scale insects ( Coccidae and Kermesidae ). It occurs commonly in deciduous forests, spruce forests, orchards, and on ornamental trees infested with scale insects ( Hoebeke and Wheeler 1991). It has been recorded from various hardwood trees, including Colorado blue spruce ( Picea pungens ), white spruce ( Picea glauca ), Norway spruce ( Picea abies ), oak ( Quercus spp. ) and American basswood ( Tilia americana ) ( Hoebeke and Wheeler 1991; Gønget 2003), and can be found generally on scale insect-infested plants. Adults have also been found on flowers of midland hawthorn ( Crataegus laevigata ); they have also been recorded to overwinter in bark cracks or in the empty ovisacs of scale insects ( Gønget 2003). This species is reported to eat a hole in the semisoft exoskeleton of a female scale insect and then lay an egg inside the brood chamber of the scale, closing the wound with a secretion ( Howden 1992). Oviposition begins in May shortly after oviposition by the scale insects. The adult beetle lays one egg in the ovisac of the female scale insect and there the larva develops. Pupation takes place in June-July inside the ovisac, and adults emerge a few weeks after and either feed on honeydew or the eggs and remains of other scale insects ( Gønget 2003). This species was intentionally introduced to the eastern United States in the late 1970’s to control scale insects that were considered pest species, though some authors speculate they were introduced as early as the late 19 th century ( Hoebeke and Wheeler 1991). In Europe, 15 scale insect species have been recorded as prey of A. nebulosus , three of which are considered economically significant species in the United States: Parthenolecanium corni (Bouche) (Coccidae) , Physokermes hemicryphus Dalman (Coccidae) , and Eulecanium tiliae Linnaeus (Kermesidae) ( Hoebeke and Wheeler 1991).

Phenology. The only known Wisconsin specimen was collected in July.

Collecting methods. The single Wisconsin specimen examined during this study from Dane County represents a NEW STATE RECORD. It was collected by beating branches of basswood ( Tilia americana ) along the shore of Lake Monona in Madison, in a mixed hardwood forest.

Figures

Figures 13–14. Anthribus nebulosus Forster. 13) Habitus, lateral view. 14) Habitus, dorsal view. Figures 15–16. Euparius marmoreus (Olivier). 15) Habitus, lateral view. 16) Habitus, dorsal view.