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The overwintering strategy of the anholocyclic aphid Cinara tujafilina

The main strategy allowing aphids to survive winter is egg‐laying. However, anholocyclic species that breed parthenogenetically throughout the year are forced to overwinter as active morphs. Cinara tujafilina (del Guercio, 1909) (Hemiptera, Aphidoidea, Lachnidae) is an anholocyclic species infesting mainly the twigs of Thuja orientalis L. Laboratory and the field experiments reported in the present study contribute towards a description of the life strategy employed by this species in winter. In winter, C. tujafilina produces three to five generations that infest the roots of the host plant. During the growing season, nine or 10 generations that feed on the above‐ground parts of the plant are produced. The main factor that triggers C. tujafilina to change the feeding site is temperature. At 13 °C, aphids migrate from leaves to the main trunk. At 0 °C, first‐ and second‐stage nymphs descend underground and feed on roots. The developmental pattern of C. tujafilina on roots in winter shows that the growth, life span and fecundity of the winter generations do not differ significantly from the generations produced in spring and autumn. The third root‐infesting generation (G3) shows the highest developmental parameters, such as the highest fecundity, a longer reproduction period and no post‐reproduction, indicating the optimal adaptation to living in soil in winter. The life‐cycle strategy enables anholocyclic populations to survive winter and to infest plants very early in spring, which gives them an advantage over species that overwinter as eggs.