Chromosomes of Belonocnema treatae Mayr, 1881 (Hymenoptera, Cynipidae)

Chromosomes of the asexual and sexual generation of the gall wasp Belonocnema treatae Mayr, 1881 (Cynipidae) were analyzed. Females of both generations have 2n = 20, whereas males of the sexual generation have n = 10. Cyclical deuterotoky is therefore confirmed in this species. All chromosomes are acrocentric and form a continuous gradation in size. This karyotype structure is probably ancestral for many gall wasps and perhaps for the family Cynipidae in general. Chromosome no. 7 carries a characteristic achromatic gap that appears to represent a nucleolus organizing region.