Effect of cone size on adult and larval foraging behavior of Strobilomyia neanthracina and Strobilomyia appalachensis (Diptera: Anthomyiidae)
1998
Fidgen, L.L. | Quiring, D.T. | Sweeney, J.D.
A 2-yr field study was carried out to determine if adult female cone maggots, Strobilomyia neanthracina Michelsen and Strobilomyia appalachensis Michelsen, oviposit preferentially on longer rather than shorter cones of white spruce [Picea glauca (Moench) Voss], and black spruce [P. mariana (Miller) Britton, Sterns & Poggenberg], respectively. The study also examined if resources increased with cone size and were limiting in small cones, and whether maggots feed mainly in sections of the cone where seeds are heaviest. Females of both species laid more eggs on longer cones than shorter cones. Number of seeds per cone and number of seeds eaten per cone were positively related to cone length. However, the proportion of seeds eaten per cone was negatively related to the number of seeds per cone in only 1 of 2 yr for white spruce and in neither year for black spruce, providing only very weak support for the prediction that resources were limiting in small cones. We evaluated the influence of cone length and seed position within cones on seed weight for white spruce only. Seed weight was positively related to cone length and was heaviest in the central sections of the cone. Larvae consumed the fewest seeds in the basal sections of the cone but nearly equal proportions in the central and apical sections. Our results demonstrate that the foraging behavior of adult females and larval cone maggots results in larvae consuming more and bigger seeds during development.
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