A General Relationship between Adult Weight and the Reproductive Potential of Aphids

Abstract

(1) Using data from over ninety aphid species living on some 120 different host plants, a negative exponential relationship between adult weight and embryo number is described which transcends the influence of both aphid species and host-plant. (2) There is no evident seasonal trend in this relationship but the rate at which the number of pigmented-eyed embryos increases as alate weight increases rises noticeably from June onwards. (3) Adult alate aphids contain more well-developed embryos as a proportion of total embryos, than do apterous aphids and have a short-term reproductive advantage. This is not the case, however, if total embryo content is used as an index. (4) As adult size increases the number of embryos plateau. Consequently, the number of embryos per unit adult body weight declines as adult size increases. Apterous aphids always have more embryos per unit weight than alate aphids of the same size. A ten-fold increase in body weight yields at least a four-fold decline in the number of embryos per unit body weight. (5) Over the whole season adult alatae have a mean weight of 0.79 mg with thirty-two embryos of which seven are pigmented. Apterae weigh 1.49 mg with fifty-five embryos of which ten are pigmented.