Field observations, laboratory rearing and descriptions of immatures of the planthopper Hyalesthes obsoletus (Hemiptera : Cixiidae)

The cixiid planthopper Hyalesthes obsoletus Signoret is an efficient vector of the stolbur phytoplasma, the cause of various crop diseases. In the fie ld, this monovoltine species feeds on a wide variety of woody and herbaceou s plants. It overwinters as larvae on the roots of its host plants. During this study, we collected adults mainly from lavender (Lavendula angustifoli a Miller), bindweed (Convolvulus arvensis L. and C. sepium L.), hoary cress (Cardaria draba L.), and occasionally from plantain (Plantago cynops L.), toadflax (Linaria striata L.), bedstraw (Galium verum L.), and mountain sav ory (Satureia montana L.). Fertility of field collected females from sites at two different elevations differed significantly. Fertility at 300 m (50. 6 eggs per female; N = 28) was more than twice that at 900 m (22.8 eggs per female; N = 19). Only one specimen of the species was found to be parasiti zed by an undetermined species of Dryinidae (Hymenoptera). H. obsoletus was reared in controlled conditions on lavender. Unlike in the field, larvae d eveloped in the laboratory at the base of the host plant and on basal shoot s. Egg incubation averaged 7 +/- 1.2 weeks (N = 10). Total development time from egg to adult averaged 27 +/- 4 weeks (N = 5) on lavender. A morpholog ical description of the five instars is provided. The study was supplemente d by scanning electron microscopy. Particular attention was paid to the str ucture of the wax-plates and the absence of compound eyes in the early larv al stages.