FEEDING EFFECT OF THE NEEDLES OF SCOTS PI NE UNFAVORABLE TO THE SAWFLY DIPRION-PINI L (HYM, DIPRIONIDAE) ON THE DEVELOPMENT OF 2 LEPIDOPTERA THAUMETOPOEA-PITYOCAMPA SCHIFF (LEP, THAUMETOPOEIDAE) AND GRAELLSIA-ISABELLAE GRAELLS (LEP, ATTACIDAE)

This paper presents the first results of feeding bioassays performed w ith Scots pine clones, more. or less favourable to the sawfly Diprion pini L., on the caterpillars of two lepidopteran species: Thaumetopoea pityocampa Schiff., the pine Processionary, an important defoliator o f mediterraneans forest and Graellsia isabellae Graells, a rare specie s, protected in Prance. Such studies are important in regard to breedi ng forest plants resistant to insect pests. A first experimentation wa s concerned with survival and development rate of Processionary larvae during the fall of 1992, on Scots pine clones in natural conditions. A second experiment dealed with some biological characteristics of G. isabellae (survival, sex-ratio, development rate, chrysalid weight). C aterpillars derived from a rearing population were fed with cut twigs from the hitching to cocoon spinning, in an outside shelter. consumpti on of the clones unfavourable to D. pini affected both species. T. pit yocampa mortality increased and its larval development slowed down. G. isabellae larval development slowed down and its chrysalid weight dec reased. Survival rates of the protected species were not changed.