Automictic parthenogenesis in the parasitoid Venturia canescens (Hymenoptera : Ichneumonidae) revisited

Both arrhenotokous and thelytokous reproduction are known to occur in the p arasitoid wasp Venturia canescens. The cytological mechanism of thelytoky w as previously reported to involve the formation of a restitution metaphase after the reduction division, but the exact nature of the subsequent divisi ons, whether reductional or equational, remained unclear. We reinvestigated the cytological mechanisms in a thelytokous strain collected in France. Ou r observations confirm previous results, but an equational and not a reduct ion division was observed after restitution. This type of reproduction can be classified as central fusion automictic parthenogenesis. In two arrhenot okous strains the normal pattern of oogenesis and syngamy of Hymenoptera wa s observed. In addition, we used PCR amplification to show that thelytoky i n V. canescens is not caused by Wolbachia bacteria. The results are discuss ed in relation to maintenance of heterozygosity and female sex.