Abstract
The karyomorphology and morphometrics of chromosomes in brain cells of fourth-instar N. lugens Biotype 1 nymphs were studied. The following features were noted: mitotic index 67%, normal diploid complement 2n=30; karyotype formula, 28 autosomes, plus XX(_??_) or XY(_??_). Males had symmetrical chromosomes with higher relative mean lengths than the females' asymmetrical chromosomes.
Mitotic chromosomes of brain cells possessed diffuse centromeres or were holocentric. During regular mitosis, prophase had the longest duration, followed by telophase. Metaphase and anaphase were short duration stages. At prophase, 8 differentiating forms of nuclei were observed.
The karyological changes in the basic diploid number were either increases (agmatoploidy) or decreases (hypoploidy) in chromosome numbers. Hypoploidy was more frequent than agmatoploidy.
