Relationships between Development Time, Reproductive Period, Fecundity and Longevity at the Within–individual Level in the Cowpea Aphid Aphis craccivora Koch (Homoptera: Aphididae)

Abstract

The cowpea aphid or groundnut aphid Aphis craccivora Koch (Homoptera: Aphididae) is often a serious pest of legume crops like cowpea and faba bean. The internal biological or life history traits, such as development, fecundity and longevity, are of particular importance to understand and predict population dynamics of pest insects. The present study focused on the individual variation and within-individual correlations between or among such important traits in A. craccivora. For this purpose, aphids were individually reared and observed throughout their lifetime. The results revealed that pre-viviparity period, i.e., the time required for the first offspring production after adult molting, correlated positively with the developmental time but negatively with the reproductive period, i.e., the number of days in which the aphid produced the offspring. The reproductive period correlated negatively with the development time and, curiously, positively with the lifetime fecundity. Thus, the aphids that develop faster reproduce for a longer period of time but produce fewer offspring. The post-reproductive period, i.e., the number of days in which adult female remained live after the last offspring production, positively correlated with the total fecundity, suggesting a disappearance of the reproductive cost. A significant negative correlation was also detected between the lifetime fecundity and reproductive period, demonstrating a cost of reproduction. We discussed the factors affecting individual variations in the life history parameters of aphids and the trade-offs between the parameters.