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.), Calloso-
bruchus 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.