Calosoma (Ctenosta) roeschkei Breuning, 1927

Length 18-25 mm. C. roeschkei is closely related to C. scabrosum and C. orientale but it has more transverse pronotum, less restricted behind, with straighter not arcuate rear sides and its upper body has lighter color with bronze luster.
C. roeschkei is also superficially similar to Calosoma (Campalita) chlorostictum as for the sculpture of elytra of triploid and homodynamic type and for the bronzed color of the upper side of the body. However, it is easy to distinguish between the two, carefully considering their body shape (C. roeschkei has the elytra visibly convex on their rear part) and the other characters that distinguish the subgenus Ctenosta, namely, the chaetotaxy (no seta exists close to basal angles of the pronotum) and the form of the pronotum, with the basal angle almost absent.
Breuning (1927: 185) described the specimens from the Usumbara mountains in Tanzania, near the Kenyan border, as a new population of C. scabrosum that he named C. scabrosum var. roeschkei.
In the description are mentioned: pronotum more straight behind, with less pronounced rear angles; somewhat flatter elytra, wider at the shoulders; bronze color of the upper side of the body, brighter on the margin and coppery foveae on the primary intervals. Jeannel (1940: 128), by interpreting the original description, expressed the opinion that these specimens belonged instead to C. orientale, that we now know is an Asian species and is not found in Africa. On the contrary all these characters seem rather to refer to the species that later he himself described as C. aethiops and the holotype of Breuning and all the specimens from Tanzania, Kenya and Somalia we examined present these characters. Therefore, Breuning identified for the first time the species that Jeannel described again thirteen years after, and the name roeschkei has priority over aethiops.
Lastly Hackel & al. (2016) reviewed the type of C. aethiops (=C. roeschkei) of Jeannel and, comparing the shape of the apex of aedeagus, they have identified this specimen with a male of C. imbricatum ottentottum, a little larger than average.
In the same publication, the Authors state the allopatry of C. roeschkei and C. scabrosum and by that fact they conclude that C. roeschkei is a geographic subspecies of the latter, occupying the southern part of its distribution area. The morphologic differences between the two species are in fact considered insignificant and not constant.
Actually, Breuning (1927: 185 and 1928b: 96) had thought of C. scabrosum roeschkei as vicarious of C. scabrosum in East Africa up to Ethiopia (Addis Ababa), where would be the contact area between the two supposed populations. Nevertheless, even assuming a misidentification of the holotype of C. aethiops, there are no doubts about the correct identification of the other specimens of the the typical serie. In fact, Jeannel attributed all these specimens to Ctenosta based on their chaetotaxy and, more precisely, on the lack of the rear pronotal bristle (always present in C. imbricatum) and on the presence of the brushes on the inner side of the male median and hind tibiae (absent in C. imbricatum).
Consequently, taking into account the data given by Jeannel in his description and the more recent findings, the area of geographical distribution of C. roeschkei is much wider than supposed by Breuning and in the northern part it largely overlaps with that of C. scabrosum.
It is difficult to interprete the citations of Jeannel of C. orientale from Eritrea (Tessenei) but he cites his C. aethiops (= C. roeschkei) also from Chad and more specimens were recently found in Niger, as well as in Ethiopia, Sudan, and Somalia, where C. scabrosum also is present, although it is not known that the two taxa were ever caught mixed together, except for a few references relating to the area between Agadez and Arlit (https://www.insecte.org/forum/viewtopic.php?t=193243).
In conclusion, the likely sympatry advises against considering C. roeschkei as a geographic subspecies of C. scabrosum.
C. roeschkei is found in Tropical Africa south-east of 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); Vad Medani (Häckel et al, 2016: 15)
Tanzania. Usumbara (holotype of Calosoma scabrosum roeschkei NBC), Natron Lake (ex coll. Battoni); Arusha reg., Mto Wa Mbu (SB).

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, 13-14.5.1988, Bruschi & Vigna

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