Effect of prey density the biology and functional response of Chrysoperla carnea
Muhammad Adnan and Ashraf Khan
Effect of prey density on biology and functional response of green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) was studied in the laboratory of Entomology Section of Agricultural Research Institute, Dera Ismail Khan at 25±1 ºC, 65±5% RH and 10:14 light : dark regime. Newly emerged larvae of C. carnea were fed 20, 30, 40, 50, 60, 70, 80, 90 and 100 fresh eggs of Sitotroga cerealella (Lepidoptera: Gelechiidae) in a small plastic bottles. It was observed that the prey density had a significant effect on positive consumption rate, development and fecundity of C. carnea. In general maximum consumption with shortest developmental time, maximum fecundity and longest adult longevity were observed as prey density increased. In all treatments, the predatory potential was high when the prey density was raised. Daily predation rate of C. carnea increased slowly during the first two instars and reached to its peak in the third larval instars. Although, C. carnea completed its development at all prey densities, the increase in prey densities reduced developmental time and mortality. Lacewing larvae provided with an overabundance of S. cerealella eggs developed faster than the larvae provided with fewer eggs. Lacewing fed during larval stage with 20 eggs/day showed the lowest fecundity with the increase in prey density. A smaller intrinsic rate of increase was due to the fact that the population fed at a low prey density had prolonged developmental time, the higher mortality rate in immature stages as well as a low daily rate of progeny.