Chromosomal studies in some Indian Lepidoptera

Abstract

1. Cytological studies have been carried out during spermatogenesis of fifteen species. 2. A peculiar synizesis phase occurs normally in the early prophase stage of primary spermatocytes. 3. The homologous chromosomal threads undergo a longitudinal pairing during synizesis. 4. Typical diplotene stage has not been discovered; instead, a diffuse phase intervenes between pachytene and diakinesis. 5. In the diakinetic bivalents the presence of one or two completely terminalized chiasmata can be justified. There are a few instances, however, where certain bivalents are precociously resolved intou nivalents disclosing most probably a failure of chiasma-formation in them. The question, therefore, whether definite chiasmata are formed in Lepidoptera cannot be answered with absolute certainty. 6. By a comparative study of the chromosomal garnitures in the congeneric forms investigated herewith, such as Vanessa indica and V. kashmirensis, and Earias insulana and E. fabia, it has been concluded that a number discrepancy in related species must be attributed to fusions and fragmentations of original chromosomes and not to polyploidy. 7. A male homogamety occurs in all the species studied. 8. Any relationship between a sex-chromosome pair and the nucleolus could not be established.