Abstract Karyotypes of four species of the genus Metaphycus Mercet, 1917, namely, M. flavus (Howard, 1881) and M. luteolus (Timberlake, 1916) (both have n = 10 and 2n = 20), M. angustifrons Compere, 1957 (n = 9 and 2n = 18) and M. stanleyi Compere, 1940 (n = 5 and 2n = 10) were studied. The latter chromosome number, n = 5, is the lowest known one for the family Encyrtidae. A karyotype with n = 10 is considered ancestral for the genus Metaphycus. Karyotype evolution in this genus is likely to have occurred through chromosomal fusions.