Temperature and Prey Density on Bionomics ofCoccinella septempunctata(Coleoptera: Coccinellidae) Feeding onAphis gossypii(Homoptera: Aphididae) on Cotton

Abstract

Life history parameters of Coccinella septempunctata L. feeding on Aphis gossypii Glover on Gossypium hirsutum L. were determined in 2 experiments. The 1st experiment addressed the effect of temperature (15, 20, 25, 30, and 35 ± 0.5°C) on C. septempunctata bionomics supplied with unlimited food. The 2nd experiment addressed the effect of food quantity on the beetle’s bionomics at 25°C. Relationships of life cycle parameters with abiotic and biotic factors were described by mathematical equations. C. septempunctata developed most rapidly at 35°C, with a preimaginal period of 10.8 d. Survival from egg to adult was highest at 25°C (47%). Oviposition was greatest at 25°C, with a lifetime oviposition of 287.4 eggs per female and a mean oviposition rate during the reproductive period of 22.4 eggs per female per day. Threshold temperatures for development of the respective stages ranged from 10.9 to 13.9°C, with 12.6°C for the entire life span. The thermal constant was 42.0, 103.7, 63.6, and 302.9 DD for eggs, larvae, pupae, and adults, respectively. Over the range of prey densities tested, a 3.5-fold increase in prey density resulted in a 2-fold reduction in larval development time and a 3-fold increase in larval survival. A 2-fold increase in prey density brought about a 2-fold increase in lifetime oviposition and mean oviposition rate.