Observations on the biology of Ceutorhynchus trisignatus Gyllenhal (Col. Curculionidae).
Ceutorhynchus trisignatus Gylh. feeds on Cynoglossum officinale, to which plant it seems to be restricted. Observations in 1974-76 in the area of Baruth, in the German Federal Republic, showed that larvae were present from late May or early June in swellings in the epidermis of the stalks. They later penetrated into the stalks and fed on the pith. They reached the roots in July and from them entered the soil, where they constructed cells in which they pupated after a few days. Dissections of cells showed that emergence to the adult stage occurred at the end of July or the beginning of August, with the pupal stage lasting 14-16 days. Adults were present by early August but remained in the pupal cells until mid-September, after which they buried themselves deeper in the soil. Field observations supporting these observations are reported. The total period spent in the food-plant was thus about 35 days.