Bionomics and Karyotypic analysis of two species of Caccobius (Scarabaeinae: Scarabaeidae: Coleoptera) detected by standard staining, C-banding and AgNOR-banding

Out of 16 species of caccobius available in India, 9 are found in Haryana and 6 in Kurukshetra. The Karyotypic characterisation of two species of Caccobius, C. ultor and C. vulcanus belonging to subfamily Scarabaeinae was undertaken using standard staining, silver staining and C-banding. Both of the species were comprised of 20 chromosomes in karyotype with meioformula, 9AA+Xyp. Modal chromosome number and meta-, submeta- centric nature revealed the conservative nature of the subfamily Scarabaeinae. The analysis of constitutive heterochromatin (CH) revealed small centromeric bands in spermatogonial metaphase and small blocks located in the terminal regions of dumb bell shaped bivalents in metaphase I. At the pachytene stage of prophase I, silver staining revealed dense spots associated with nucleolar organizer regions. In addition to this, the Chiasma frequency and terminalisation coefficient were also calculated, illustrating the close relationship of Caccobius ultor and C. vulcanus with other Scrabaeinae species. In beetles as well as in other insects, the chromosome structure, pattern of constitutive heterochromatin distribution, and position of the nucleolar organizer region are all key factors in speciation.