Parallel trends of chromosomal evolution in Aphidococca are discussed, based on the catalogue of chromosomal numbers and genetic systems of scale insects by Gavrilov (2007) and the new catalogue for aphids provided in the present paper. To date chromosome numbers have been reported for 482 species of scale insects and for 1039 species of aphids, thus respectively comprising about 6% and 24% of the total number of species. Such characters as low modal numbers of chromosomes, heterochromatinization of part of chromosomes, production of only two sperm instead of four from each primary spermatocyte, physiological sex determination, "larval" meiosis, wide distribution of parthenogenesis and chromosomal races are considered as a result of homologous parallel changes of the initial genotype of Aphidococca ancestors. From a cytogenetic point of view, these characters separate Aphidococca from all other groups of Paraneoptera insects and in this sense can be considered as additional taxonomic characters. In contrast to available paleontological data the authors doubt that Coccinea with their very diverse (and partly primitive) genetic systems may have originated later then Aphidinea with their very specialised and unified genetic system.

The karyotype of the root aphid Tetraneurella akinire was analysed by means of C, G, and NOR banding. The overall base pair distribution was investigated after CMA 3 and DAPI fluorochrome staining. Both C and G treatments revealed a well defined banding pattern on the X and A1 chromosomes. C-bands showed a marked polymorphism in both size and number, even within the same individual. NOR banding produced a precipitation of silver on one telomere of the X chromosome, which also showed bright fluorescence after CMA 3 staining. Treatment with DAPI uniformly stained all chromosomes. Neither CMA 3 nor DAPI showed bright fluorescence overlapping the C-positive bands. It can be concluded that T. akinire chromosomes present a cluster of GC-rich DNA sequences located on one telomere of the X chromosome, whereas the AT-sequences are regularly arranged along the chromosome axes and not grouped into well defined clusters.

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The holocentric mitotic chromosomes of Megoura viciae, a species that has been little studied cytogenetically to date, have been characterized by applying G, C, AluI, and HaeIII banding techniques. C bands have shown the best defined patterns, particularly on the X chromosome. This chromosome, on the other hand, behaved as the most reactive to the various treatments. Uncondensed, prometaphase X chromosomes showed a number of heterochromatic bands, interspersed among the euchromatin, which fused together during metaphase condensation. AluI and HaeIII treatments also produced reproducible banding patterns. These data permit an accurate identification of the X chromosome as well as of the autosomal pairs 1 and 2, and facilitate the construction of nonambiguous karyotypes. They will also stimulate studies on the organization of chromatin in holocentric, holokinetic chromosomes. Finally they could also promote research on chromosomal rearrangements that have occurred during the course of speciation and evolution of aphids, since these kinds of events may be significantly affected by the condition of chromosomal holocentrism.Key words: aphids, holocentric chromosomes, chromosome banding, heterochromatin.

The life history of sexuparae and sexual morphs of woolly apple aphid (Eriosoma lanigerum Hausmann) is reported from Simla Hills. Sexuparae are alate parthenogenetic viviparae and produce the sexuals (males and oviparaej.The reproductive potential of sexuparae is much lower as compared to that of virginoparae. Sexuals are apterous and have degenerated mouth parts. An ovipara lays only one egg. All these morphs undergo four moults resulting in five instar stages.