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Three hymenopteran species - the ichneumonids Amblyteles armatorius and Diphyus quadripunctorius, and the proctotrupid Exallonyx longicornis - are most frequently cited from all over Europe as executing their inactive hypogean ecophase in caves. Yet, little is known about their environmental requirements during their summer quiescence and/or winter diapause; only limited data are known from Western and Eastern Europe. In this investigation, the sojourn of hymenopterans in hypogean environments is ecologically evaluated on the basis of data obtained from 63 systematically investigated caves and artificial tunnels in central and northern Slovenia, as being representative of the Central European countries. Nine environmental parameters measured at the resting sites of individuals were subjected to Principal Component Analysis (PCA). The species differ significantly from each other on ecological parameters: the euryecious A. armatorius occupies a narrow central position with respect to environmental requirements in caves; the montane D. quadripunctorius exhibits the best, and the lowland E. longicornis the feeblest adaptation to hypogean environments. In contrast to Western and Eastern Europe, in the central countries, the three hymenopteran species prefer dormancy habitats other than caves. These regional differences deserve more attention in future investigations of European hypogean fauna. [ABSTRACT FROM AUTHOR]