In the surroundings of Ostrava city (the north-eastern part of the Czech Republic), large damage caused by Norway spruce saw-flies pseudocaterpillars has occurred during last 50 years. However, no precise study of species diversity and bionomy of these insect species have been made there. Křístek (1980) has studied the Norway spruce saw-flies and their pseudocaterpillars in the whole territory of Moravia (23 sites - except the surroundings of Ostrava) and only part of the results has been published (Křístek 1973). Abundance of the saw-flies was characterised as a latency in majority of sites.
Kolubajiv (1958) has studied the cocoons of saw-flies in this area. During the period 1949 - 1952, about 70% of cocoons belonged to the gregarious spruce saw-fly (Pristiphora abietina (Christ, 1791)), but in the nearby Beskydy Mts. the proportion of this species was 10-18% only. The age of the forest stands where the samples were taken was not mentioned.
Kaněčka (1995) carried out an basic (till now, unpublished) investigation by using the photoeclectores and the method of knocking down of pseudocaterpillars.
I present the main results of my research made in 1998 in this paper.