Flight regulation in the green spruce aphid (Elatobium abietinum)

In Britain the flight of alate parthenogenetic viviparae of Elatobium abietinum was found to occur only in early summer. Data for this study were extracted from suction trap catches and weather records obtained from meteorological stations adjacent to the traps. The duration of the flight period increased with latitude. At 51° N 95 % of the trap catch was taken in 24 days and at 55° N in 32 days. A flight threshold temperature of 12–13°C was deduced from trap catches taken within the forest crop. Displacements in median flight days at various sites in Britain could be related to values of accumulated day-degrees but not to differences in photoperiod. The median flight day can be predicted empirically by accumulating day-degree values over 8°C from 1 January up to a total of 115 day-degrees. The implications of seasonal flight activity on crop reinvasion is discussed.