Predation of brevicoryne brassicae and aphis craccivora by eriopis connexa depending on availability

Abstract

Predator species under field conditions can face different and variable densities of prey species. This work evaluated the functional response of the neotropical lady beetle Eriopis connexa (Coleoptera: Coccinellidae) subjected to different densities of the aphids Brevicoryne brassicae and Aphis craccivora (Hemiptera: Aphididae). Thus, predation rates were analyzed of fourth-instar larvae and one-day old adults of the lady beetle preying upon the aphids at constant densities of 20, 40, 50, 60, and 70 aphids with 15 repetitions per density. The aphids were offered on 5 cm leaf discs of each plant host. The handling times and attack rates were 0.03 h-1 and 0.27 h-1 for larvae and 0.03 h-1 and 0.15 h-1 for adults fed B. brassicae and 0.59 h-1 and 0.35 h-1 for larvae and 0.70 h-1 and 0.95 h-1 for adults fed A. craccivora, respectively. Both larva and adult lady beetles increased predation rate as a function of prey density offered, with an estimated maximum number of prey consumed of 30.3 and 31.6 B. brassicae and 36.3 and 34.6 of A. craccivora by larva and adult lady beetles at the highest prey density, respectively. In conclusion, larvae and adults of E. connexa exhibited a type II functional response.