none. The total of nine species of larval parasites (eight species of ichneumon flies and one species of tachina flies) were reared at five localities in the Czech Republic in 1976 to 1984 from large populations of eonymphs of web-spinning sawflies of the Cephalcia Pz. genus (with more than 95% prevalence of the C. abieties L. species). In these populations there were also two predacious parasitic species in web-spinning sawfly larvae: they were from the Muscidae family and their imagoes were hatching at the same time as tachina fly imagoes. In the CR the following species of larval parasites are living in web-spinning sawflies of the Cephalcia Pz. genus and mainly in the C. abieties L. species: ichneumon flies Homaspis rufinus Grav.), H. narrator (Grav.), H. subalpina Schm., Olesicampe monticola (Hdwg.), Sinophorus crassifemur (Th.), Xenoschesis fulvipes (Grav.), Ctenopelma nigrum Hlmgr. and Notopygus nigricornis Kriechb., and tachina flies Myxexoristops abietis Hert. Larvae of the species Phaonia basalis Zett. and Ph. errans (Meig.) from the Muscidae family are predacious parasites in the eonymphs of web-spinning sawflies. Most of the above-mentioned larval parasites of web-spinning sawflies of the Cephalcia Pz. genus occurred at all test localities at the height zone of 580 to 840 m above sea level. Some species are rare and they occur only in some regions which are ecologically most favourable. E. g. the ichneumon flies Homaspis subalpina Schm. and Notopygus nigricornis Kr. were reared only at the lowest altitudes. The ichneumon fly Ctenopelma nigrum Hlmgr. occurred in the host population at greater heights above sea level also only exceptionally, and just in certain years. At lower altitudes this species was mostly dominant. A species with the highest ecological valence is the ichneumon fly Homaspis rufinus (Grav.), occurring at all height zones. The most frequently dominating species was only the ichneumon fly Olesicampe monticola (Hdwg.), mainly at greater heights. The species Sinophorus crassifemur (Th.) was quite abundant in the parasite spectrum mostly at lower altitudes, similarly like the ichneumon fly Xenoschesis fulvipes (Grav.). The tachina fly Myxexoristops abietis Hert. was found to be a parasitic species of web-spinning sawflies also at all localities of observation and is one of the most important parasites of the host, especially at lower heights. Two new predacious parasites of eonymphs of the Cephalcia Pz. genus from the Muscidae family were found. They play their role mainly in the period of retrogradation of the pest populations at sites with the highest temperatures. The total parasitism in the host population given by the complex of larval parasites (including the activity of the two less numerous predacious species) was decreasing along with the higher altitudes above sea level from the average value of 10.4% at the lowest height to the average value of 3.4% at the greatest height of a mountain site.