Soil samples were collected from the whole territory of the Czech Republic, and the presence of entomopathogenic nematodes from the families Steinernematidae and Heterorhabditidae was evaluated by Galleria traps method. Of the 342 samples studied, 53.8% were positive for entomopathogenic nematodes with only one positive for the heterorhabditid, Heterorhabditis megidis Poinar, Jackson ct Klein. 1987. Of steinernematid species, Steinernema kraussei (Steiner, 1923), Steinernema felliae (Filipjev, 1934), Steinernema affine (Bovicn, 1937), Steinernema intermedium (Poinar, 1985), Steinernema bicornutum Tallosi, Peters et F.hlers, 1995, and Steinernema sp. belonging to “glaseri" group were recovered. With several exceptions the nematodes occurred in all the ecosystems, subecosystcms and habitats studied. They were more frequently found in samples from tree than open habitats, from light than heavy soil, and their incidence was ubiquitous, rather than patchy. Dependence of entomopathogenic nematodes on insect incidence seemed to be elementary for both their incidence and abundance. The sampling sites with moderate to severe insect abundance were 66.5 % positive for nematodes while those with slight or no visible insect abundance only 15 %.
The star formation process in a molecular cloud core is effectively halted when the newly born stars remove the remaining gas cloud out of the region. We present analytical and numerical calculations
of the dynamical evolution of a young cluster, which we allow to deviate from or oscillate around exact Virial Equilibrium (V.E.), during slow and rapid gas removal. Our conclusion is that
deviations from V.E. can influence the final dynamical state of the 'nakeď cluster significantly.