Immanus Hulcr & Cognato, 2013 : 100

Beaver, R. A., Sittichaya, W. & Liu, Y., 2019, A review of the genus Immanus Hulcr & Cognato with a key to species (Coleoptera: Curculionidae: Scolytinae: Xyleborini), Zootaxa 4585 (2), pp. 378-386 : 379

Genus Immanus Hulcr & Cognato, 2013: 100

Type species: Xyleborus colossus Blandford, 1896: 207 . Original designation.

Diagnosis: The females of the genus can be distinguished from those of other xyleborine genera by the following combination of characters: Large, robust species, 4.0‒9.0 mm long, with declivity usually either obliquely or steeply truncate (strongly convex in one species), often with a raised rim. Pronotum anterior margin with a row of 4‒6 coarse asperities, which may be fused to form a carina; pronotal disc asperate to base; mycangial tufts absent. Scutellum flat, flush with elytra. Procoxae contiguous; protibia with reduced or without socketed teeth, its anterior margin irregular, its posterior side flat without granules.

The male has been described for only three species: I. colossus ( Schedl 1942c) , I. desectus ( Eggers 1923) and I. sarawakensis ( Schedl 1942b) . They are characterised by a large, shovel-shaped pronotum, concave dorsally, and with a median rounded or pointed projection of the anterior margin. Photographs of the three species’ males are available at URL: http://xyleborini.myspecies.info/. The males are not considered further here.

Description: Hulcr & Cognato (2013) give a detailed description of the genus, and we do not repeat it here. We note that the addition of further species to the genus requires small modifications to the generic description. The upper part of the eye may be larger than, approximately equal to, or smaller than the lower part in different species. The first segment of the club may cover two-thirds of the posterior surface of the club so that the second and third segments of the antennal club are displaced apically on the posterior side. The elytral declivity is convex in one species in which the posterolateral declivital costa extends only to interstriae 7 and not around the whole declivity. Interstriae 1 may not be widened towards the elytral summit. The size range varies from 4.0‒9.0 mm.

Relationships: Recent phylogenetic analyses of Xyleborini ( Cognato et al. 2011, Gohli et al. 2016, Johnson et al. 2017) have not included species of Immanus . Based on morphological characters, the most closely related genus is Ambrosiodmus , in which many of the species were placed by Wood and Bright (1992). Ambrosiodmus shares a pronotum asperate to the base with Immanus , but the latter genus is distinguished by the following characters (those of Immanus given first): 1) anterior margin of the pronotum bears 4‒8 distinctly larger asperities, which may be fused to form a carina vs marginal asperities not larger than those on anterior slope; 2) elytral declivity obliquely truncate in lateral profile, sometimes with a row of teeth or an elevated costa encircling declivity, sometimes excavated (one exception with a steep convex declivity) vs declivital profile convex, steep near apex. posterolateral costa never extending beyond interstriae 7; 3) protibial denticles usually reduced or absent, reduced on meso- and metatibiae vs protibial denticles large, longer than wide, not reduced on meso- and metatibiae; 4) large size, minimally 4.0 mm long, with most species more than 5 mm vs small size, usually 2.5‒3.5 mm long and not exceeding 4.5 mm.

Distribution: The genus is confined to the region from South-East Asia ( Thailand and Vietnam), the Philippines, Malaysia and Indonesia to New Guinea and Australia.

Biology: Little is known of the biology of Immanus . It is presumed that it generally resembles that of other xyleborine genera ( Kirkendall et al. 2015). The species are inbreeding ambrosia beetles with a female-biased sex ratio. Both adults and larvae feed on ambrosia fungi growing on the walls of the gallery constructed by the parent female in the stem of the host tree. The gallery system is known for only a single species ( I. desectus ). It is branched in one plane, and probably lacks brood chambers. It is likely that all species are polyphagous, attacking a wide variety of host trees in tropical rain forest. Despite their size, the species are rarely collected, and are not known to be of economic importance.