Summary Eurydema pulchrum Westw. and Bagrada cruciferarum Kirkadly (Pentatomidae) show 2nϭ14ϭ12AϩXY. Autosomes show gradation in size, X is of medium size while Y is the smallest element. Both X and Y are positively heteropycnotic in diffused stage but become isopycnotic in diplotene stage and divide equationally during meiosis-I. At metaphase-II, X and Y get associated, the association being strong forming a pseudobivalent XY in Eurydema pulchrum while weak in Bagrada cruciferarum. A definite pattern of arrangement of the chromosomes is seen at metaphase-II.Cletus bipunctatus Westw. and Serinetha augur Fabr. (Coreidae) show 2nϭ17ϭ14Aϩ2mϩXO and 2nϭ13ϭ10Aϩ2mϩXO respectively. The complement in both the species is conspicuous by the presence of 2 microchromosomes and absence of Y element in males. Microchromosomes form achiasmatic bivalent at meiosis-I. X undergoes equational division at metaphase-I while at metaphase-II it remains outside the metaphase plate and is added to one of the pole as a precocious element in Cletus bipunctatus and as a laggard in Serinetha augur.Key words Chromosomes, Meiosis, Pentatomidae, Coreidae.The family Pentatomidae, one of the major families of Heteroptera, includes shield-shaped bugs which are commonly called stink-bugs due to the presence of stink glands. Members of the family Coreidae are called squash bugs or leaf-footed bugs and are characterized by the presence of scent glands on the thorax. Family Pentatomidae is noted for its extreme karyotypic conservation. Earlier knowledge about the cytology of this family is largely due to the contribution made by Gupta (1950), Manna (1951, Rao (1954), Dutt (1955, Hughes-Schrader and Schrader (1957), Parshad (1957b) and Schrader and Hughes-Schrader (1958). The family Coreidae is characterized by the presence of a pair of very small chromosomes which behave differently from both autosomes and sex-chromosomes during meiosis (Wilson 1905). The present paper includes the study of diploid complement and behavior of autosomes and sex chromosomes during meiotic cycle in four North Indian heteropteran species belonging to Pentatomidae and Coreidae. Materials and methodsSpecimens of Eurydema pulchrum Westw., Bagrada cruciferarum Kirkadly. (Pentatomidae) and Serinetha augur Fabr. (Coreidae) were collected from Patiala (Punjab) while those of Cletus bipunctatus Westw. (Coreidae) were collected from Palampur (Himachal Pradesh). Male bugs of each species were dissected to take out the testes which were fixed in ethanol : glacial acetic acid (3 : 1) and air dried chromosomal preparations were stained in carbolfuchsin stain.