Calosoma (Ctenosta) roeschkei Breuning, 1927

Length 18-25 mm. C. roeschkei appears closely related to C. scabrosum but its pronotum is more transverse, with the sides more regularly curved, less narrowed towards the rear; its elytra are slightly wider and less constricted at the apex and the upper part of the body is of a lighter bronze colour.
Breuning (1927:185) described specimens from the Usumbara Mountains in southern Tanzania, near the Kenyan border, as a new population of C. scabrosum which he called C. scabrosum ssp. roeschkei. The description mentions: the pronotum straighter behind with less pronounced posterior angles; slightly flatter elytra, wider at the shoulders; bronze color of the upper body, more vivid on the margin and coppery foveas on the primary intervals.
Subsequently Jeannel (1940: 127) described a new species Ctenosta aethiops, insisting on some particularities of chaetotaxy but also reporting all the morphological characters already highlighted by Breuning describing C. scabrosum ssp. roeschkei, while expressing the judgment that the specimens attributed to the latter instead belonged to C. orientale, which we now know is an Asian species and is not found in Africa.
In conclusion, the characters used in Jeannel's description are found in all the specimens that Breuning attributed to C. scabrosus roeschkei. Breuning identified the taxon for the first time and the name roeschkei has priority over aethiops redescribed thirteen years later. Furthermore, more recently Hackel & al. (2016) examined in deep the type of Jeannel's C. aethiops and, by comparing the shape of the apex of the aedeagus, identified this specimen with a slightly larger than average male of C. imbricatum hotentottum.
In the same publication, the Authors declare the allopatry of C. roeschkei and C. scabrosum and therefore conclude that C. roeschkei is a geographical subspecies of the latter, occupying the southern part of its range. The morphological differences between the two taxa are in fact considered insignificant and not constant.
Indeed Breuning (1927: 185 and 1928b: 96) had thought of C. scabrosum roeschkei as the vicariant of C. scabrosum in East Africa as far as Ethiopia (Addis Ababa), where it would have been the area of contact between the two presumed populations. However, the geographic range of C. roeschkei is much larger than initially assumed and in part overlaps that of C. scabrosum in the northern part.
Jeannel mentions his C. aethiops (= C. roeschkei) from Chad and other specimens have recently been found in Niger, as well as in Ethiopia, Sudan and Somalia, where C. scabrosum is also present, even if it is not known that the two taxa have ever been captured mixed together, except for some references related to the area between Agadez and Arlit (https://www.insecte.org/forum/viewtopic.php?t=193243).
In conclusion, the probable sympatry and, in any case, the lack of specimens with intermediate morphological characteristics in the contact areas, advise against considering C. roeschkei a geographical subspecies of C. scabrosum.
Finally, we observe that in the past C. aethiops (= C. roeschkei) has been sometime confused with Calosoma (Campalita) chlorostictum to which it is superficially similar to as regards the sculpture of the elytra of triploid and homodynamic type and for the bronzed color of the upper part of the body. However it is easy to distinguish between the two, carefully considering the shape of the body (C. roeschkei has the elytra visibly convex posteriorly) and the other characters distinguishing the subgenus Ctenosta, i.e. the chaetotaxy (there is no bristle near the basal angles of the pronotum) and the shape of the pronotum, with the basal angle almost absent.
C. roeschkei is found in tropical Africa southeast of the Sahara. We know it from: Niger, Burkina Fasu, Chad, Sudan, Eritrea, Ethiopia, Somalia, Kenya, Tanzania.

Examined specimens and literature’s data:
Burkina Faso. Essakane (SB)
Chad. Mortcha (Jeannel, 1940: 127), Ennedi (Jeannel, 1940: 127)
Eritrea. Asmara (RS), Tessenei (Rougemont, 1976: 247)
Ethiopia. Gamu Gofa: Woito (SB); Hararge: Dire Daua (sub C. aethiops Jeannel, 1940: 127); Shewa: Addis Ababa (Breuning, 1928b: 96), Buffet d'Aouache (Rougemont, 1976: 247); Sidamo: 40 km W Konso 600m (SB)
Kenya. Coast prov: NW of Garsen (SB), N. of Bura (SB), Kasigau Teita Hills (SB), Turkana Mts Murueris (sub orientale Jeannel, 1940: 129), Taveta (Breuning, 1927: 186), Kilifi (www.inaturalist.org); North Eastern prov: El Wak (Häckel et al, 2016: 15, TL), Garissa (www.ebay.it); Northern prov: Tsavo East Voi (SB); Amboseli nat. park (EM, SB); Eastern prov: prov: Mwingi (SB), Marsabit (SB), Sosoma (Häckel et al, 2016: 15); Rift Valley prov: Archers Post (SB, TL), Ngurunit (Ebay.com)
Niger. Arlit (Agadés reg.) (DP)
Somalia. Jowhar (Vil. Duca Abruzzi) (sub C. rugosum, MFi); Abarey, Shabelle Swamps (AVT, SB); Afgoi (AC, AVT, EM); Genale (AC); Balad (AVT); Berbera (Breuning, 1928b: 96)
Sudan. White Nile (Jeannel, 1940: 127); Gazira, Vad Medani (Häckel et al, 2016: 15); Red Sea prov. 190 km E of Atbara. Khor Adarot (SB)
Tanzania. Arusha reg., Mto Wa Mbu (SB); Natron Lake (ex coll. Battoni, Vigna Taglianti & Bruschi, 1988: 243); Tanga reg. Usumbara mts. (holotype of Calosoma scabrosum roeschkei) (NBC)

Notes: C. roeschkei is diurnal as well as nocturnal, and it is mainly a soil dweller. Active individuals, that are winged and attracted to light at night, were captured during or immediately after the different raining periods that characterize the monsoon climates: in Somalia from March to May and in November December; in Niger and in Ethiopia (Rougemont, 1976: 247) from August to September; in Tanzania and Kenya from October up to January.
The species was named after Hans Friedrich Wilhelm Roeschke (1867-1934), a German entomologist primarily interested in beetles.

Calosoma (Ctenosta) roeschkei ♂ Breuning, 1927 Usumbara (holotype of C. scabrosum roeschkei) (coll. Naturalis Biodiversity Centre, Leiden) photo by the courtesy of Ben Brugge

Calosoma (Ctenosta) roeschkei ♂ Breuning, 1927 Somalia: Lower Shebeli, Abarei, Lake Joware, 13-14.V.1988, Bruschi & Vigna

Calosoma (Ctenosta) roeschkei ♀ Breuning, 1927 Somalia: Lower Shebelli, Afgoi, Lafoole (Fac. Agric.), at light, 7.V.1988, Bruschi