A Simple Method for Estimating the Number of Eggs of the West Indian Sweetpotato Weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae), Using a Measuring Pipette and Cylinder.

Abstract

Abstract:In the mass rearing of Euscepes postfasciatus using artificial diets, a method for estimating the number of eggs is essential for monitoring egg-collection efficiency and controlling egg-seeding density on the diets. To develop a simple method, we first analyzed the relationship between the volumes of eggs aspirated into a 1-or 2-ml measuring pipette and the number of eggs in it. A significant difference in the pattern of increase in egg number, along with the increase of volume, was found between the two pipette types. Linear and quadratic regressions fitted well for the 1-and 2-ml pipette data, respectively (R 2 Ͼ0.97). To extend the egg-number estimation to a larger quantity of eggs, we performed similar analyses using a 5-ml measuring cylinder. Here, the number of eggs contained was determined using the above measuring pipettes and regressions. A linear regression of the estimated number of eggs on volume fitted well (R 2 ϭ0.99). The results show that the number of E. postfasciatus eggs can be estimated precisely using measuring pipettes or cylinders. This study also showed that the pattern of increase in egg number differs depending on the measuring equipment, which should be considered for establishing egg-number estimation methods for other insects.

High Population Density and Egg Cannibalism Reduces the Efficiency of Mass-Rearing inEuscepes postfasciatus(Coleoptera: Curculionidae)

“…After a few min, we collected the eggs from the boundary between the salt-water and the freshwater by pipette. The number of eggs per container was estimated by the method from Ohno et al (2006). When there were very few eggs and the number could not be estimated by this method, we counted the eggs directly.…”