Trichogramma semblidis [Chalcidoidea: Trichogrammatidae] as a parasite of the bark beetle eggs [Coleoptera: Scolytidae]

It has been found thatTrichogramma semblidis (Aurv.) parasitizes the eggs ofleperisinus fraxini (Panz.),L. orni (Fuchs) andHylesinus crenatus (Fabr.) in typical variant ofCircaeo-Alnetum Oberdorfer 1953 in the Laski Experimental Forestry near Kepno. Thorough studies were conducted on exposed European ash logs and split wood in 3 methodical variants. The analysis of the galleries ofLeperisinus fraxini has showed that the average egg infestation amounted to 14.1%, 13.0% and 11.1% respectively. The egg infestation of individual gallery systems in the exposed control logs and split wood ranged between 2.7–51.2%, 1.2–44.1% and 1.7–69.2%, respectively, in different variants and the average effectiveness of the parasite amounted to 12.7% of the host egg mortality in 1970. Earlier observations and analyses of the gallery systems made on the ash trunks and branches in 1967 and 1968 showed 80.0% and 98.0% infestation of the eggs ofL. fraxini and 10.0% and 1.5% infestation of the eggs ofL. orni. Separate developmental stages of the parasite, the behaviour of the latter and penetration of the gallery systems were observed too. The most important data on the host species ofT. semblidis have been compared.