Contrasting population growth parameters of the aphidophagous Scymnus nubilus and the coccidophagous Nephus reunioni

Compared to coccidophagous ladybirds, aphidophagous ladybirds develop and live faster. They also produce more eggs at a faster rate. As we wanted to know how these traits influence population dynamics, we have determined the population growth parameters for the aphidophagous Scymnus nubilus Mulsant (Coleoptera: Coccinellidae) and the coccidophagous Nephus reunioni Fürsch (Coleoptera: Coccinellidae) fed Rhopalosiphum padi (L.) (Hemiptera: Aphidoidea) and Planococccus citri (Risso) (Hemiptera: Coccoidea) respectively under controlled laboratory conditions. Net reproductive rate, intrinsic rate of natural increase, and finite rate of increase were all significantly higher, and generation time and doubling time were both significantly shorter in S. nubilus compared to N. reunioni. The reproductive output of the aphidophagous species rapidly reaches a peak and then sharply declines while it is regularly distributed throughout adult life in the coccidophagous predator. A significant difference in late survival was found, with S. nubilus exhibiting higher survival. Adaptation to the consumption of aphids and coccids occurred in several species during the co-evolutionary history of ladybird beetles and their prey. Thus, comparing other species would be valuable to confirm the differences reported here.