Modified method of Trypsin-EDTA G-banding was applied to the somatic metaphase chromosomes of a lepidopteran species, Ascotis imparta belonging to family geometridae. Fifth instar larvae were captured from economically important plant Ricinus communis (castor) near Brahmsarover, Kurukshetra. First the elongated karyotypable elements could be secured by application of in vitro colchicine treatment as the mitotic division was successfully arrested at metaphase stage. Both male and female karyotypes from somatic metaphases of brain ganglia revealed 2n=62. Although Giemsa-stained preparations confirmed female heterogamety with ZW: ZZ sex mechanism, this was authenticated by modified G-banding technique confirming ZZ to be the largest pair still longer than the first autosomal pair; W being comparatively smaller in between the size of 2nd and 3rd autosomal pairs. Results were compiled on the basis of Morphometric data analysis of somatic karyotypes (2n=62) including mean total length (um) and relative length percentage (RL%) of individual G-banded chromosomal elements in both the sexes. This is the first report of differential staining technique applied to a geometrid Lepidopteran species A. imparta and is worth further investigation in the field of cytogenetics.