Terminal speed and size sorting of insect eggs

Engineering data for improving the design of applicators for beneficial insect's eggs and facilitating egg cleaning at mass-rearing plants are presented. A vertical air column was developed to measure terminal speed of beneficial insect eggs. Raw material was sorted into fractions according to terminal speed and photos were taken for measuring dimensions of particles. Particle distribution was evaluated for two beneficial insect eggs used in biological control (Chrysoperla rufilabris and Ephestia kuehniella eggs parasitized by Trichogramma brassicae) and for one unparasitized host eggs (E. kuehniella). Density measurements were performed as these data were required for calculating terminal speeds using the theory of free falling bodies. Unparasitized E. kuehniella and C. rufilabris eggs stored at 5°C showed constant terminal speed (1.9 and 1.34 m/s, respectively) and density (1.05 g/cm³, for both). Terminal speed of parasitized E. kuehniella eggs decreased from 1.32 to 1.06 m/s with increasing storage time (4-8 days). Photos of subsamples suggested that aerodynamic cleaning could be used for improving the quality of raw eggs. Density evaluations showed that parasitized eggs can be separated by flotation in water. Calculated terminal speeds were accurate for unparasitized eggs but were 10-20% overestimated for parasitized eggs.