Karyotype differences among four species of Callosobruchus Pic (Coleoptera: Bruchidae)

Three species of the genus Callosobruchus are particularly common pests of stored legumes on an international scale. A fourth is closely associated with the most common. In this paper we show that they can all be separated quickly, easily and unambiguously by examination of their karyotypes. Karyotypes obtained from developing embryos of Callosobruchus analis (F.), Callosobruchus chinensis (L.), Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) are illustrated and compared, using both plain (Giemsa-stained) and C-banded preparations. The karyotypes of all four species are distinctive, and the greater detail resulting from the use of hypotonic inflation, air-drying methods, compared with earlier squash techniques is shown to be crucial to revealing the differences between the species and to resolving some of the discrepancies in published information. We have found no evidence of intraspecific variation so the technique offers a quick and inexpensive way of confirming morphological distinctions.

► Karyotypes were obtained from developing embryos of four Callosobruchus species.
► Callosobruchus analis, C. chinensis, C. maculatus and C. subinnotatus are illustrated and compared.
► All the karyotypes comprise 9 pairs of autosomes and sex chromosomes which are Xy (♂) or XX (♀).
► Each species has a distinctive karyotype with features enabling it to be identified.