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In forests of Pinus nigra Arn. 147 egg‐batches of T. pityocampa were collected at different locations in Bulgaria in September‐October 1991 and March and June 1992. Directly after collection all batches were put singly into test tubes with cotton stoppers and stored under laboratory conditions at 20–22°C. Oviposition always started from the base towards the top of the needle. The emergence of egg parasitoids were controlled almost daily and they were counted and identified. The eggs from which parasitoids emerged were marked for further studies. After removing the scales and opening the eggs, the impact of the parasitoid species was evaluated by their meconia and remains. Ooencyrtus pityocampae (Mercet) was observed as the most abundant egg parasitoid, followed by Anastatus bifasciatus (Fonsc.) and Baryscapus servadeii (Dom.). The hyperparasitoid, Baryscapus transversalis Graham was recorded for the first time in Bulgaria and the polyphagous species Macroneura vesicularis (Retzius) was collected in Bulgaria for the first time from an egg‐batch of T. pityocampa. Trichogramma sp. was obtained in small amounts, too. Total mortality of host eggs varied from 34% to 48%; the mortality rate due to parasitism was 24.5% to 38.9%. The emergence dynamics of the egg parasitoids was studied under laboratory conditions, and the distribution of the egg parasitoids in the egg‐batches was recorded in detail. Additionally, the structure of the meconia of A. bifasciatus and M. vesicularis was described.

Field investigations were carried out on the parasitism of egg‐batches of T. wilkinsoni Tarns near Lahav, Israel, in 1989. Egg‐batches were collected and studied under laboratory conditions in Hannover. For ovipositions, the host preferred the marginal, especially the southern exposed parts in the forest and in the trees. At Lahav the peak time of egg deposition durated from 13th‐23th of September. The parasitoid impact could be recorded with 38.6%. The most frequent parasitoid was Eutetrastichus servadeii (Dom.), followed by Ooencyrtus pityocampae Mercet. The distribution of the parasitoids in the field was correlated with that of the egg‐batches of the host. O. pityocampae showed a better ability in finding egg‐batches than E. servadeii. O. pityocampae parasitized eggs more frequently at the tip of the batch, whereas E. servadeii parasitized more homogeneously across the egg‐batch. In the laboratory at a temperature of about 19 °C the parasitoids emerged from egg‐batches at the same time as they were expected to emerge in the field in Israel. Among the temperature the age of the host and hyperparasitism are discussed as determining factors for the diapause of O. pityocampae. Zusammenfassung Zur Parasitierung der Eigelege des Pinienprozessionsspinners, Thaumetopoea wilkinsoni Tams (Lep., Thaumetopoeidae) im Lahav‐Gebirge von Israel Im Jahre 1989 erfolgten Freilanduntersuchungen über die Eiparasitoiden des Pinienprozessionsspinners Thaumetopoea wilkinsoni Tams in der Näbe von Lahav (Israsel) sowie anschließend einjährige Beobachtungen der gesammelten Gelege im Labor in Hannover. T. wilkinsoni bevorzugte zur Eiablage südlich exponierte Lagen im Wald und am Baum. Die Hauptablagezeit dauerte 1989 vom 13. bis zum 23. September. Der mittlere Parasitierungsgrad der Eigelege betrug 38,6 %. Das Parasitoidenspektrum bestand im wesentlichen aus Eutetrastichus servadeii (Dom.) und Ooencyrtus pityocampae Mercet. E. servadeii war die häufigere Art. Die Verteilung der Parasitoiden im Gelände ähnelte der der Wirtseigelege. Am Südrand des Waldes waren die höchsten Dichten der Parasitoidenarten anzutreffen. O. pityocampae wies ein besseres Wirtsfindungsvermögen als E. servadeii auf. Innerhalb der Gelege parasitierte O. pityocampae am häufigsten Eier an der Spitze, während E. servadeii zu Beginn der Saison häufiger an der Basis der Gelege auftrat, sich aber mit zunehmender Expositionszeit homogener verteilte. Trotz einer konstanten Labortemperatur von etwa 19 °C schlüpften die Parasitoiden zur gleichen Zeit, zu der sie auch in Israel im Freiland erschienen wären. Für O. pityocampae werden als induzierende Diapausefaktoren, neben der Temperatur, das Alter der Wirtseier sowie Hyperparatisierung diskutiert.

The pine processionary caterpillar Thuumetopoea pityocumpa is one of the pine defoliators of high economic importance, especially in forests of the Mediterranean. Various species of Pinus serve as food plants to this polyphagous forest pest. To observe the effects of different pines on the development and mortality, newly hatched larvae from egg batches collected at Kassandra/Greece were treated with 13 different species of pines and with one species of larch. Pinus mugo Turra was taken as the standard host plant and the effects shown by the caterpillars feedin on other pine needles were compared with those feeding on P. mugo. The pine twigs used for t8e current study were made available by *Berggarten" of Hannover.Cateroillars fed with the needles of P. strobus L.. P. oarvzfloru S. & Z.. P. cembru L.. P.wullichiaha Jacks and Lurix kaempferi (Lamb.) Car;. sh'owed a delayed larval development.Moreover, a 100 Yo mortality could be observed within the first instar in the larvae feeding on P. purvifora and within the second instar in those feeding on P. strobus and L. kaempferi. The larvae fed with P. cernbru needles could live till third instar. Though some of the mature larvae fed on P. wallichiunu (= P. excelsu Wall.) migrated into the soil (larval mortality 96.7 Yo), none of the pupae could survive.The difference in the mean pupal weight could not be statistically verified in pupae of those cater illars which had fed on P. contortu Dougl., P. nigru Am., and P. leucodermis Ant., although the larvafmortality was recorded to be 11.7 YO, 43.3 YO and 33.3 YO, respectively. The mean pupal weight of other groups ranged from weakly to highly significant level.