Functional response of larval and adult stages of Hippodamia variegata (Coleoptera: Coccinellidae) to different densities of Aphis fabae (Hemiptera: Aphididae)

Abstract

We compare the efficiencies of different stages of Hippodamia variegata (Coleoptera: Coccinellidae) preying on Aphis fabae (Scolpoli) (Hemiptera: Aphididae) by estimating the functional responses of all stages. The experiments were carried out on leaf disks in petri dishes with 1520 replicates. Our results revealed that all larval instars and adult males and females of H. variegata exhibited type II functional responses on different densities of prey. The rate of searching efficiency and handling time were estimated as 0.063 h -1 and 6.933 h for first instar, 0.059 h -1 and 3.343 h for second instar, 0.103 h -1 and 1.909 h for third instar, 0.114 h -1 and 0.455 h for fourth instar, 0.159 h -1 and 1.194 h for male, 0.093 h -1 and 0.409 h for female, respectively. Thus, handing time decreased from first instar to female. Handling times of males were significantly greater than those of females. The most effective stages of H. variegata were females, fourth instars, and males. The efficiency of females was nearly three times greater than that of males. The voracity of larval stages and male and female adults of H. variegata were estimated as 2.93, 5.85, 12.13, 45.13, 18.33, and 44.60 (aphids/d), respectively. © 2010 Entomological Society of America.