Karyotype and achiasmatic female meiosis in Helicoverpa armigera (Hübner) and H. punctigera (Wallengren) (Lepidoptera: Noctuidae)

The economically important pest species Helicoverpa armigera and H. punctigera have a karyotype consisting of 31 pairs of chromosomes. The chromosomes are in a graded series of sizes such that pairs cannot be differentiated. Cytological evidence suggests that female meiosis is achiasmatic. Precocious separation of bivalents into univalents at metaphase I was observed in some spermatocytes of H. punctigera. This species also had a consistently greater number of bivalents with fully terminalised chiasmata in each spermatocyte at male metaphase I than H. armigera.Key words: Lepidoptera, Helicoverpa, achiasmatic meiosis, karyotype.