Powell W
Department of Forestry, The University, Old Aberdeen, Scotland.
Ann Appl Biol. 1974 Sep;78(1):27-37. doi: 10.1111/j.1744-7348.1974.tb01482.x.
Laboratory investigations into the low-temperature tolerance of the green spruce aphid, Elatobium abietinum, revealed that the insect was killed by freezing. Aphids and host Sitka spruce needles showed similar seasonal changes in supercooling ability. A noticeable increase in this ability occurred between June and October. Aphids were more susceptible to low temperatures when attached to the plant. It is suggested that mortality resulted from ice which formed in the sap of the host needles and spread into the feeding aphids via their mouthparts. Neither the chlorotic banding of needles, caused by aphid feeding, nor needle length affected needle supercooling. Increased duration of exposure increased the probability of freezing of supercooled needles at low temperatures. A small percentage of first-instar nymphs supercooled to much lower temperatures than the remainder of the population. These were newly born nymphs whose high supercooling ability markedly decreased when they began to feed.
对云杉绿球蚜（Elatobium abietinum）低温耐受性的实验室研究表明，该昆虫会被冻死。蚜虫及其寄主西加云杉针叶的过冷却能力呈现出相似的季节性变化。6月至10月间，这种能力显著增强。蚜虫附着在植物上时对低温更敏感。据推测，死亡是由于寄主针叶汁液中形成的冰通过蚜虫口器扩散到取食的蚜虫体内所致。蚜虫取食导致的针叶黄化带以及针叶长度均不影响针叶的过冷却。暴露时间延长会增加低温下过冷却针叶结冰的可能性。一小部分一龄若虫的过冷却温度比种群其他个体低得多。这些是新出生的若虫，它们开始取食后，其高过冷却能力会显著下降。
