Cadoderus Faust

Yunakov, Nikolai, 2012, 3535, Zootaxa 3535, pp. 1-104 : 5-6

The Cadoderus Faust generic complex

Distribution. Weevils of this generic complex occur in East Africa. They are represented in young mountains such as Kilimanjaro, Aberdare, and the comparatively old massifs of Chyulu Hills and Eastern Arc Mountains. The latter compound massif is significantly highlighted by maximal species richness and may be considered as a hot spot of biodiversity of this group. The ranges of most known species are rather restricted, and species appear to be strictly endemic to isolated mountain ranges or their portions, but it can not be excluded that such small ranges result from the small amount of material available. Nevertheless, material examined shows that a number of species almost never extend beyond the limits of one or two neighboring mountain ranges. This is most apparent in North and South Pare Mountains and Nguru Mountains where 2–3 sympatric species occur on each ridge. Other isolated mountains also have endemic species. The Usambara Mountains consist of western and eastern massifs separated from the Pare Mountains by the narrow valley of the Mkomazi River. Each massif contains endemic species including the genus Oncophyes — endemic to Usambara. The range of Cadoderus is much broader than that of Oncophyes and limited by the Usambara and Nguru Mountains ( Tanzania) and Ruvube River ( Burundi). Sphrigodellus has the maximal range. Its occurrence is limited to the north by the Aberdare mountain range, to the south by the Udzungwa Mountains, and to the east by the Indian Ocean. The western limit of the range of Sphrigodellus is unclear due to the lack of material from the Rift Valley. Only one species is known so far from Mt. Kilimanjaro. Species inhabit xerothermic and wet forests, from sea level up to 2800 m elevation.

Biology. The biology of these species is still poorly studied; the beetles apparently inhabit the canopy level of big trees and middle size shrubs. Interaction with host plants is also not very clear; adults have been recorded on plant species from several families: Psychotria spp. , Mystroxylon aethiopicum , Myrsine africana etc. Oviposition has not been studied but, considering that the ovipositor is heavily sclerotized and the spiculum ventrale possesses a narrow knife-shaped lamella, it may be presumed eggs are deposited in narrow gaps in "suspended litter", i.e. aggregations of lichens/moss/small orchids, dead leaves between tree branches. Descent of beetles to the ground occurs only as an emergency. As it was observed by the author, the species of Cadoderus and other forest dwelling groups of Embrithini do not possess an advanced armor, common in Cryptorhynchinae, that could protect the weevils from ants, particularly dorylines. It is likely, that for this reason in the middle montane forest belt, where ants are abundant, the diversity of forest floor leaf litter Entiminae is low. The subfamily is represented mostly by miniaturized unarmored Hypsomias Aurivilius, 1910 , Tapinomorphus Hartmann, 1904 and endogean blind or microphthalmic species of Dysommatus Marshall, 1933 . By contrast, the diversity and abundance of leaf litter dwelling species among armored Molytinae and Cryptorhynchinae are higher than in Entiminae. At higher elevation, where the (doryline) ants are less abundant, i.e. in the three vegetation belts dominated by Erica arborea , Hagenia abyssinica and Afroalpine belts (2700–4600 m a.s.l.) the diversity and abundance of soil dwelling Entiminae is higher compared to poorly represented Molytinae and Cryptorhynchinae.

Coloration. These weevils exhibit a cryptic color pattern formed by a combination of differently coloured scales. The well-defined green and brown stripes and spots have the effect of obscuring the outline of the beetle so that it blends in with the natural environment (small spots of lichens, moss and algae on leaves and branches). Unidentified species of Conoderinae (figs 41, 42), collected in the same biotope, exhibit the same general color pattern as Sphrigodellus and Cadoderus , but the number and arrangement of the stripes is different. This convergent crypsis contrasts with another phenomenon described for species of Baridinae, where beetles have a remarkable, extravagant appearance that also seems to result in a noticeable loss in the ability of natural enemies to discriminate less striking details ( Prena 2010).