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Octotemnus and relatives

the species of Octotemnus occur throught Palearctic and Indo-Pasific regions only one species ( Octotemnus laevis Casey, 1898) distributes in the Nearctic region that seems to be synonym of Octotemnus glabriculus (Gyllenhal, 1827). Then Octotemnus glabriculus can suppose a cosmopolite species.
In the tribe Orophiini the genus Octotemnus is closely related to the genus Hyalocis Kawanabe,1993 by similarities in the tibia,maxillae and male genitalia.
The resemblance among tibial spines is also observed in the genus Xylographus and some other genera of other tribes.
Therefore this character may not always reflect their phylogenetic relationships. Then it cannot be considered as phylogenetic character between genera.
Though the maxillary galea is usually semioval in the family, some genera belonging to the tribe Orophiini have elongate (Octotemnus) and triangular (Hyalocis) ones.
A tendency of expansion of the maxillary galea seems to indicate an affinity on their phylogenetic relationship. The other character is male genitalia that is extremely simplified i genus of Octotemnus simple oval to pentagonal plate such as Hyalocis yakushimensis Kawanabe,1993 and Octotemnus laminifrons seems to be also reflected on the close relationship between two genera.
bill-shaped process of male abdominal sternite seems to be one of the synapomorphic characters which is only recognized among the two genera. Octotemnus and Ropalodontus.
host fungi of Octotemnus usualy is Coriolus verscolor and its related species but they scarcely prefer the fungus species with ligneous fruiting body such as Fomitopsis, Fomes,Ganoderma and so on.Their host preference is striking contrast to those of the genus Xylographus and Ropalodontus which prefer the ligneous and hard fungi.
These differences of their host preference are also recognized as the morphological difference in the adult mandibles.


Reference: Kawanabe 2002