MULTIPLE-CHROMOSOME SEX SYSTEMS IN THE DARKLING BEETLES BLAPS GIGAS AND BLAPS GIBBA (COLEOPTERA, TENEBRIONIDAE)

We have studied mitotic and meiotic chromosomes in the males of two sp ecies of Blaps: B. gigas and B. gibba. Karyological characteristics su ch as the occurrence of a multivalent configuration at diakinesis and two types of metaphase-II spreads support the notion that multiple-chr omosome sex systems involving five chromosomes in B. gigas and eight c hromosomes in B. gibba have developed in these species. Results obtain ed by means of silver staining and C-banding techniques suggest that t he complex sex systems occurring in B. gigas and B. gibba may have ori ginated from exchanges of terminal ribosomal genes among the Y chromos ome and some autosomes.