Structure, hatching rate and parasitism of egg-batches of Thaumetopoea pinivora (Tr.) (Lep. Thaumetopoeidae) near the Baltic Sea

Abstract

Studies were carried out on egg material of Thaumetopoea pinivora (Treitschke, 1834) collected on Pinus sylvestris L. in a forest near Kaliningrad in September 1989 and 1990. Hatching of the caterpillars was observed at spring time of the following year from the egg-batches collected in 1989 and 1990. The hatching period was about two weeks. The egg-batches were formed from the tip to the bottom of the needle to 98% and situated in the middle of the needle length in most of the cases. For egg laying only one or two needles were used per individual. Often egg deposition started on one needle and used later another. The fertility can be more than 90% and egg parasitation rate was very low in both years. The only recorded egg parasitoids belonged to the genus Kratoysma (Eulophidae). Egg parasitoids did not influence population dynamics of the host. The egg-batches were arranged in 6 to 8 almost lìnear rows. A highly significant correlation (r = 0.90-0.94) could be found between the total number of eggs and the produci of batch length and number of egg rows; the number of eggs per 1 cm egg row varied from 8.56 to 8.91. In the two years under study, the mean number of eggs per batch was 164 and 165, respectively.