Unicellular algae and diatoms (Bacillariophyta) in particular, have attracted increasing attention as the objects of biotechnology. Diatoms are known to produce mucopolysaccharides, fats, and fat like sub stances suitable for production of biodiesel, unusual pigments (e. g., marennine), and nanosized siliceous structures. It should be noted that only few diatom species out of great number living on the Earth are used in biotechnology. About 100000 species of diatoms occur in nature. The use of diatoms in biotechnology is restricted by little studied life cycle and biology of reproduction. This review summarizes data on biological properties of diatoms, which should be taken into account when they are used as the objects of culturing and particularly as clones.

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An annotated list of ten species of digger wasps from ten genera is given. The lectotype of Plenoculus murgabensis (Gussakovskij, 1928) is designated; this species is newly recorded from Kalmykia (Russia) and Uzbekistan.

Abstracts-The species boundaries and biogeography of two closely related diatom species, Nitzschia longissima (Bréb.) Grunow and N. rectilonga Takano, are described. Based on the structure and morphological features of frustule valves, a reliable distance between these two species has been determined. It is shown that there is a reproductive barrier between the two species. The distribution of N. longissima and N. rectilonga and the range and character of their natural habitats have been analyzed.

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