Population Dynamics Features of Willow-feeding Aphids

Willow-feeding aphid colonies were sampled on scattered trees (Salix alba) from April until November, in 1999. The collected individuals belonged to 9 aphid species of 3 families (Lachnidae, Chaitophoridae, Aphididae). The aphid populations showed two peaks in May and in October. The indirect negative effect of the rainfall seems to be responsible for this temporal pattern. The Shannon diversity also exhibited spring and autumn peaks during the year. The willow-feeding aphid guild seasonally rearranged, different species were dominant in each period. Four types of population dynamics of the 9 species were established based on the abundance changes. The time of appearance of different morphs in two dominant species was compared, they belonged to Pterocomma genus. In spring, there were uncoordinated schedule in the development of populations of P. pilosum konoi and P. rufipes, the different morphs of P. pilosum konoi increased earlier. In autumn both species reached their peaks simultaneously, but there were fewer individuals of P. pilosum konoi for a longer time. This species was more vulnerable to aphid parasitoids in each season