Chortastus Schaufuss, 1905

Jordal, Bjarte H., 2025, Taxonomic revision of the rare Afrotropical genus Chortastus Schaufuss (Coleoptera: Scolytinae), Zootaxa 5647 (1), pp. 77-84 : 78-83

Chortastus Schaufuss, 1905

Afrochramesus Schedl, 1971 , synonym by Wood, 1984

Type species: Chortastus camerunus Schaufuss, 1905

Diagnosis. Antennal club asymmetrically attached to the funicle, flattened, with an oblique partial septum, sutures faint or distinctly marked, asymmetrically procurved; funiculus 6-segmented; eyes deeply and broadly emarginated on upper third of its anterior margin; labial palp segment 1 as long as 2 and 3 combined, ligula not developed; maxillary palp segments of similar length, setae along the lacinial edge long and thin; pronotum smooth, distinctly constricted on its anterior third; basal margin of elytra crenulated, recurved in middle, scutellar shield not visible; tibiae with 3–5 short denticles at the apical margin, apex in meso- and and particularly the metatibiae forming a corbel-like structure; proventriculus with anterior plate as long as posterior part, with transverse rows of small teeth, median suture not present.

Phylogeny. Browne (1973) suggested that this genus is closely related to Phloeosinus Chapuis having fairly similar antennae, tibiae and proventriculus. He also remarked that it shares some similarities of the tibiae and antennae with Phrixosoma Blandford. Other authors place the genus in Polygraphini based on the invisible scutellar shield, smooth pronotum and flattened antennal club (e.g. Wood 1986). In recent molecular phylogenetic studies ( Jordal & Cognato 2012; Pistone et al. 2018), however, Chortastus verrucosus sp. nov. (named as Chortastus medius, PoCho 01) did not group closely with any of these taxa, or any other genera, and the status of the genus therefore remains enigmatic.

Biology. Sexual dimorphism is striking with females having a simple unmodified frons and males having either a tuft of long setae or concavities with lateral tubercles. Dissection of C. verrucosus sp. nov. revealed a female with spermatheca, which had a simple frons, and a tuft of setae attached to the gula on the underside of the head. The gular tuft is also seen in females of C. orientalis and is a character of uncertain function that appears in a handful of species across the entire subfamily.

Schedl (1959) described the reproductive biology in two species breeding under the bark of Staudtia trunks and large branches ( Myristicaceae ). Monogamous pairs were formed in which the female made primarily two longitudinal egg tunnels away from a central mating niche. Based on illustrations the brood sizes could be more than 100 larvae in one family.

Key to species

1. Large species,> 5 mm long; most striae distinctly impressed, interstriae 3 on declivity each with a raised ridge that midway contain a median pointed tubercle; elytra nearly glabrous, vestiture consisting of short, fine, recumbent setae ( Congo Basin)................................................................................... Chortastus camerunus

- Body length <3.5 mm; striae on disc not impressed; elytral vestiture of erect bristle-like setae........................ 2

2. Elytral declivity with a prominent ridge along interstriae 3 (expanding towards 4); strial punctures large and deep, broader than width of interstriae ( Congo Basin)...................................................... Chortastus schenklingi

- Elytral interstriae 3 on the declivity only slightly if at all elevated more than other interstriae; strial punctures narrower than interstriae........................................................................................... 3

3. Elytral declivity with interstriae 2 impressed and interstriae 3 slightly elevated, appearing sulcate; body length <2.8 mm ... 4

- Declivity with uniform interstriae; body length> 3.2 mm ( Tanzania)............................. Chortastus orientalis

4. Elytral interstriae on declivity with densely placed, sharp granules, all except interstriae 2 raised; female head on its underside with tuft of forward pointed setae ( Cameroon)...................................... Chortastus verrucosus sp. nov.

- Elytra with interstriae smooth throughout, only interstriae 3 raised ( Congo Basin)................... Chortastus minimus