A DOME-SHAPED RELATIONSHIP BETWEEN HOST-PLANT ALLELOCHEMICAL CONCENTRATION AND INSECT SIZE

A dome-shaped relationship was found between the concentration of resi n acids in larval food and the weight of female pine sawfly (Neodiprio n sertifer) cocoons. Sawflies feeding on pine needles with low to inte rmediate resin acid concentrations attained a higher weight than sawfl ies feeding on needles with resin acid levels in the lower or upper pa rt of the concentration range; cocoon weight reached its maximum at ap proximately 0.4% d.w. Cocoons were obtained by rearing larvae enclosed in sleeve cages in the field on two species of pine, Pinus contorta a nd P. sylvestris (n=15 trees with two cages per tree per pine species) . The discussion addresses the question of whether the relationship is continuous and dome-shaped or consists of one positive and one negati ve relationship at low and high concentrations, respectively. (C) 1997 Published by Elsevier Science Ltd.