Egg number quantification for mass-rearing of Aedes aegypti and Aedes albopictus: validation by direct measurement

Abstract

Mass-production of Aedes aegypti and Ae. albopictus for use in vector control programs involving the sterile insect technique (SIT) requires the standardization of rearing techniques, including the production of eggs. Following published protocols, egg quantification for both species was performed based on the weight and volume characteristics of batches of 1,000 to 27,000 eggs from insect colonies that originated from natural populations in Chiapas, Mexico. The findings were validated by direct measurement of egg dimensions. On average, Ae. aegypti eggs were ∼40% heavier and occupied ∼25% larger volume than those of Ae. albopictus (p < 0.001). Egg numbers were readily predicted by linear correlation with the weight and volume of eggs of both species (p < 0.001). Volumetric measures were significantly more consistent among replicates than the weight measurements (p < 0.02). Direct measurements revealed that the eggs of Ae. aegypti were ∼10% longer (p < 0.001), ∼13% wider (p < 0.001), and also more variable in size than those of Ae. albopictus. These species also differed significantly in egg length:width ratios (p < 0.001). We conclude that proxy indicators of egg numbers, such as weight and volume, should greatly assist in standardizing larval rearing procedures.