Terminal speed and size sorting of insect eggs

Abstract

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.

Keywords:

• Aerodynamic
• terminal speed
• Trichogramma brassicae
• Chrysoperla rufilabris
• Ephestia kuehniella
• beneficial insects

Acknowledgments

This research was supported by the MII program of Agriculture and Agri-Food Canada and Insecterra Inc. The authors thank Beneficial Insectary for providing biological material and for technical support. The authors also wish to thank M. Claude Godin for his meticulous technical assistance and Dr G. Boivin for helpful suggestions for improving the manuscript.