Karyotype analysis of three weevil species from the Genera Brachysomus (Boheman, 1845) and Strophosoma Billberg, 1820 (Coleoptera, Curculionidae).

Karyotypes of three weevil species, viz. Brachysomus dispar (2n=22, n males = 10 + X(y(p))), Brachysomus hirtus (3n=33, n females = 10 + X) and Strophosoma faber (2n=22, n males = 10 + X(y(p))) belonging to the tribes Sciaphilini and Brachyderini, were studied using the C-banding technique. The karyotype structures of the two bisexual and one parthenogenetic species are described for the first time. Most chromosomes are meta- or submetacentric. In the two species of the genus Brachysomus, the chromosomes resemble one another in having a rather small amount of heterochromatin restricted to the pericentromeric region, visible as dark stained blocks mainly during the early stages of nuclear division. Larger bands at mitotic metaphase and diakinesis occur only in Strophosomafaber. Geographic parthenogenesis in Brachysomus hirtus is briefly discussed.