Life table parameters of Cephalonomia tarsalis (Hym.: Bethylidae),‌ a parasitoid of Oryzaephilus surinamensis (Col.: Silvanidae)

Background and Objectives:

 Life table parameters are important and key tools to reveal the reproductive and population growth potential of natural enemies regarding control of their prey/host. 

Materials and Methods:

 The initial population of Cephalonomia tarsalis was collected from wheat storage facilities in Tehran province. Life table parameters of C. tarsalis on the 3th instar larvae of Oyzaephilus surinamensis were investigated using100 newly laid eggs (as a cohort) at temperature of 25±1 °C, 60±5% R.H. and photoperiod of 16:8 (L:D) hours. The daily counts of mortality and fecundity were arranged as a life table and used to calculate net reproductive rate (Ro), intrinsic rate of increase (rm), finite rate of increase (λ), mean generation time (T) and doubling time (DT).

 Results:

 As a result of this study survival rate (lx) decreased with increasing age and life expectancy (ex) at birth 43/8 days. Egg hatch rate (hx) was determined to be 0.96. As a result of this study, the gross fecundity and fertility rates were determined to be 84.74±0.61 and 81.35±0.58 and net fecundity and fertility rates were 60.9±2.03 and 58.46±1.95, respectively. The average number of eggs produced per female per day was 2.56±0.01. The intrinsic rate and finite rate of C. tarsalis on the 3th instar O. surinamensis were 0.104±0.001 and 1.11±0.001 day-1 , respectively. Time required to increase the population to the size of the net reproduction rate and doubling times were 36.2±0.065 and 6.62±0.059 days, respectively. The gross and net reproduction rate were 61.37±0.159 egg and 44.1±1.47 females/females/generation, respectively. The results of this study on the stable age distribution showed that 91.14 % and 8.02 % of the population belonged to immature stage and adults, respectively.

 Discussion:

Based on the findings, it could be concluded that C. tarsalis has a good potential to control its host, C. tarsalis.