THE VARIABILITY OF SOME PHENOTYPIC FEATURES AND LIFE CYCLE IN TWO Aphis pomi POPULATIONS FROM WESTERN ROMANIA.

This paper presents data referring to the external morphological characteristics, the biometrical measurements and the life cycle of Aphis pomi. The researches have been carried out on the orchards from the experimental fields of the Didactic Station Timiş oara (Timiş County) and Várfurile, (Arad County), 2003 2008. At the Aphis pomi species the smallest length of the body established for aphids captured in the western zone of Romania was 1.80 mm, while the biggest was 2.00 mm. Regarding the length of the head and thorax, it may be noticed that the maximum length of these parts was 1 mm, and the minimum length was 0.65 mm. The minimum width of the head was 0.20 mm and the maximum width of the head was 0.35 mm. The thorax width had a minimum of 0.60 mm and a maximum of 0.80 mm. The minimum length of the abdomen was 0.90 mm and the minimum width was 0.70 mm, the maximum length of the abdomen was 1.20 mm and the maximum width was 0.90 mm. In the climatic conditions of Romania, Aphis pomi winters in the stage of egg in October usually on the stems of apple tree. In the second decade of March, the eggs hatch out and there appears the fundatrix giving birth to one or more generations of fundatrices, which are apterous parthenogenetic viviparous females. The winged aphid migrates to other nearby host plants like pear, peach trees and other herbaceous plants growing in the vicinity of apple trees. The reproductive process continues rapidly, the populations of aphids are developing quickly in a very short time. Green apple aphids usually remain on apple plants throughout the summer and gave birth parthenogenetically to 9 12 generations. In October, Gynetypes (gynopara) give birth to wingless sexual, oviparous females, that mate with males and lay winter eggs. [ABSTRACT FROM AUTHOR]