Seasonal changes in the synusia of pine sawflies (Hym., Diprionidae) during their latency.
Seasonal changes in the abundance and dominance in the species composition of pine sawflies (mainly Neodiprion sertifer and Diprion pini) on Scots pine (Pinus sylvestris) during a period of low population density (latent phase) were studied in pure stands in southern Bohemia, Czechoslovakia. A total of 8 species was recorded in stands of different ages in 1984-88. Two significant annual peaks of larval abundance were recorded, the first during the spring feeding period in June, when several species were usually present (average 5.8 in 5 years), and the second in late August-early October (average 4.8 species in 5 years). The second maximum was divided into 2 peaks corresponding to at least 2 waves of diprionids during the summer period. The proportion of 'rare' and outbreak species was approximately balanced, the average proportion of solitary species being 57.7% of the sawfly population in the 5 years. Solitary species, especially Gilpinia frutetorum, prevailed in older stands (38-88 years old), while Neodiprion sertifer was the eudominant species in young stands. Larval feeding lasted from May to late October, but there were significant variations in the population density of individual species during the latent phase.