The Cyprus Processionary Caterpillar (Thaumetopoea wilkinsoni, Tams)

Abstract

Thaumetopoea wilkinsoni, Tams, is known only in Cyprus, where it abounds, attacking all species of pine, but chiefly Pinus halepensis, Mill.In the plains the adults emerge from the end of August to the beginning of October. The eggs are laid, shortly after emergence, in cylindrical masses round pine needles, the masses averaging 150 eggs. Only one mass is laid by each female. The incubation period is about 45 days.The five larval instars are described, as well as the differences in the habits and nests in the various instars. The length of the larval life varies from 116 to 173 days. Only in the fourth do larvae remain in the same nest throughout the instar, as they frequently migrate, moving in single file to new feeding grounds, and there construct a new nest. Six such migrations have been observed for one colony during its three earlier instars.Pupation, which commences in the plains about the middle of March, takes place in the ground in silken cocoons at a depth of ¼ to 3 inches, the pupal life lasting all through the hot weather.Altitude considerably influences the life-history—the greater the altitude the earlier the emergence of the adult and the later the pupation of the fully-grown larvae, with consequent alterations in the length of the larval periods.Of the checks, two species of Chalcid egg-parasites have been shown to occasion a parasitism of over 17 per cent., and three species of Tachinid larval parasites sometimes to occasion a parasitism of at least 30 per cent. There is also an Ichneumonid larval parasite. This latter aestivates in the pupa of its host ; the Tachinids leave their larval hosts and pupate in the nest of the processionary.Re-afforestation in Cyprus, both natural and artificial, being an urgent necessity, this processionary is of great economic importance, as stands of young trees suffer very heavily from its attacks, one colony of larvae being sufficient to strip and, if the late rains fail, to kill a small tree. The writer considers, however, that control is possible by encouraging the parasites and predators, methods for which are outlined.