In the years 1988/89,222 egg-batches of the pine processionary caterpillar Thaumetopoea pityocampa (Den. & Schiff.) collected in Greece were studied in the laboratory for one year. Data on structure and size of the batches as well as a method rendering quite accurate estimates of the number of eggs per batch are presented. Altogether 10 871 parasitoids belonging to 6 species of Chalcidoidea emerged from the samples. The three most abundant species were Eutetrastichus servadeii (Dom.), Ooencyrtus pityocampae Mercet and Eutetrastichus sp. near servadeii. In the samples collected on Kassandra (KI) and on the Peloponnes (P) in autumn 1988 shortly after oviposition, the number of emer ing primary arasitoids was largely related to the duration of field exposure of the batches. Caterpiflars hatched from 67 YO of the eg s of these sample units. In egg-batches collected on Kassandra after 7 months of exposure in the f i e d (KII) a much greater parasitoid impact was observed. Not only did they yield more adult parasitoids throughout the first year; a striking difference was the much higher proportion of eggs without hatching or emergence holes, a majority of which showed signs of parasitoid attack.Only 4 % of the eggs appeared to be sterile after one year. Host mortality in the KII egg-batches was calculated to be 63 %.
Studies on nests of the pine processionary caterpillar were carried out in different parts of Greece in the years 1985 to 1988. Most of the nests could be found at the southeast, south and southwest of pine trees. Deviations in the distribution could be due to the slope of forests and a high population pressure. Registering of temperature data verified that the inner temperature of the caterpillar nests could rise quite high. Such a warming is clearly dependent on the intensity of the insolation and the thickness of the nest webs. The biogenic heat production has not a significant role.
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