Callosobruchus rhodesianus Pic, 1902

Delobel, Alex, 2012, Bruchinae (Coleoptera: Chrysomelidae) from Socotra Island, Acta Entomologica Musei Nationalis Pragae 52, pp. 373-380 : 375

Callosobruchus rhodesianus Pic, 1902

Material examined (5 spec.). YEMEN: SOCOTRA ISLAND: Wadi Ayhaft , 12°36′38″N 53°58′49″E, 190 m, 24.– 26.xi.2003, 1 spec., D. Král leg. ( CBAD) ; Sirhin area , Dixam Plateau, 12°31′08″N 53°59′09″E, 812 m, 1.–2.xii.2003, 1 spec., P. Kabátek leg. ( NMPC) ; Firmihin , 12°28′27″N 54°0′54″E, 400–500 m, at light, 6.–7.ii.2010, 1 spec., L. Purchart & J. Vybíral leg.( NMPC) ; Aloove area , Hasan vill. env., 12°31.2′N 54°07.4′E, 221 m, 9.–10.xi.2010, 1 spec., J. Hájek leg. ( NMPC) ; Dixam plateau, Firmihin ( Dracaena forest), 12°28.6′N 54°01.1′E, 490 m, 15.–16.xi.2010, 1 spec., J. Hájek leg. ( NMPC) .

Distribution. Angola, Benin, Ivory Coast, Kenya, Senegal, Togo, Yemen, Zimbabwe. First record from Socotra Island.

Comments. Socotran specimens differ markedly from those from mainland Africa: prescutellar lobes are much less markedly convex, are covered with dense pale yellowish (instead of pure white) setation, and elytral vestiture is much less contrasted (almost uniformly pale fulvous in some specimens). Such differences in external morphology would possibly justify a separation at species level. Examination of male genitalia however shows that the aedeagus of Socotran specimens is perfectly identical with that of specimens from East Africa. The median pair of dented sclerites in the internal sac is clearly different in specimens from West Africa, so that populations from Socotra appear more closely related with Kenyan than with West African populations.

Callosobruchus rhodesianus is a well-known pest of cowpeas, Vigna unguiculata (L.) Walp. ( Fabaceae : Phaseoleae : Phaseolinae ), both in the field and in stores. According to TUDA et al. (2006), its wild populations favour dry areas with a long dry season, which explains the ability of this species to use dry and hard beans as a food source. It is also recorded from another Phaseolinae , Nesphostylis holosericea (Welw. ex Baker) Verdc. ( GILLON et al. 1992) , but its larvae can also attack members of the subtribe Cajaninae such as Cajanus cajan (L.) Millsp. AMEVOIN et al. (2005) showed that C. rhodesianus populations are outcompeted by Callosobruchus maculatus when both species coexist in the same stored seeds.