%0 Journal Article
%T The Effect of Prey Density on Life Table Parameters of Hippodamia variegata (Coleoptera: Coccinellidae) Fed on Aphis gossypii (Hemiptera: Aphididae) under Laboratory Conditions
%A Soodeh Davoodi Dehkordi
%A Ahad Sahragard
%A Jalil Hajizadeh
%J ISRN Entomology
%D 2013
%R 10.1155/2013/281476
%X Life table gives the most comprehensive explanation of the survivorship, development, and reproduction of a population. The life table parameters of ladybeetle, Hippodamia variegata (Coleoptera: Coccinellidae), on different densities (20, 40, 60, 80, and 100) of third instar nymphs of Aphis gossypii were studied in a growth chamber ( ¡ãC, % RH, and a photoperiod of 16L: 8D h). The adult preovipositional period and the total preovipositional period of female H. variegata were reduced as the prey density increased. The oviposition period was longer when prey density increased. Female longevity also increased significantly with increasing prey density. Fecundity was dependent on prey density. The lowest fecundity was obtained at density of 20 prey ( ) and the highest at density of 100 ( eggs). Intrinsic rate of increase was dependent on prey density and ranged from to £¿d£¿1 (female/female/day) with increasing prey density. Net reproductive rate and gross reproductive rate were also increased with increasing prey density. The peak reproductive values were dependent on prey density. However, mean generation time decreased as prey density increased. It was concluded that the increase in the density of A. gossypii nymphs had positive and significant effects on reproductive parameters of H. variegata. 1. Introduction Aphids are a diverse group of plant feeding insects that are predominantly found in temperate climate zones such as North America, Europe, Central, and Eastern Asia [1]. They cause damage directly by sucking plant sap, secrete honeydew resulting in development of sooty mould on leaves and shoots, and indirectly as vectors of certain plant viruses [2, 3]. The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) as a cosmopolitan and polyphagous species is widely distributed in tropical, subtropical and temperate regions. This aphid is a pest of cotton, cucurbits, and citrus and principally attacks vegetables in fields and greenhouses [4]. The lady beetles are the most commonly known worldwide beneficial insects [5]. The Coccinellids are of great economic importance in agroecosystems through their successful application in the biological control of many injurious insects [6]. The variegated lady beetle, Hippodamia variegata (Goeze), is an active predator used in the biological control of aphids in cereals and oil plants in various countries [7¨C9]. This Coccinellid, as an important aphidophagous predator in Europe [10], is widely distributed in a large portion of the Palearctic region [7]. In Australia, the ladybeetle was recorded preying on 12
%U http://www.hindawi.com/journals/isrn.entomology/2013/281476/