Age-specific functional response of Nephus arcuatus (Col.: Coccinellidae), predator of Nipaecoccus viridis (Hem.: Pseudococcidae)

This study has evaluated the age-specific functional response of the females of Nephus arcuatus Kapur, as the major predator of Nipaecoccus viridis (Newstead). The varying density of N. viridis eggs (2, 4, 8, 15, 40, 65, 90, and 115) were offered to 3 to 33 days of the lifespan of the female adults under laboratory conditions (30 ± 1 °C, 65 ± 5% RH and a photoperiod of 14L: 10D h). The age of female adults affected functional responses, its parameters (handling time (Th) and attack rates (a)), and predation rate by N. arcuatus. Females exhibited functional response type III during 16th, 24th and 28th days of their life. Conversely, the functional response during the other 30 days of female life changed from functional response type III to type II. The handling time decreased significantly from the 4th to 17th day as female age increases and then increased, whereas, the attack rates did not significantly change with higher age of the predator. The maximum attack rate values were found on the 12th, 14th, 15th, 17th, 18th, 20th and 25th days of female adults. The maximum mean predation rate was 156.6 eggs on the 17th and 18th days. Accordingly, the best time to use females of this predator in an inundative biocontrol agent is during the first 25 days of females' age, when the predator is more capable to attack the prey, especially when N. viridis is in the egg stage.