Predator’s collection
Samples of the anthocorids were collected from the wild and cultivated pistachio trees located in Kerman Province, Iran (Sirjan and Rafsanjan orchards, between 53° 26′ E and 25° 55′ N and 59° 29′ E and 32° N) by using sweeping nets and aspirator, during May 2016. Collected bugs were transferred to the laboratory of Kerman Agricultural and Natural Resources Education and Research Center and identified by the taxonomical keys of Linnavuori and Hosseini (2000) and Falamarzi et al. (2009), then A. minki pistaciae individuals were separated.
Insect rearing
Adult insects of the bugs were kept in a growth chamber at 25 ± 1 °C, 55 ± 5% R.H., and a photoperiod of 16 h:8 h (L:D). They were fed on psyllids. In order to rear this predatory bug, the Leaf-disk method was used (Mehrnejad 1998). In this method, to retain the moisture and to keep the pistachio leaves healthy, the Petri dishes were filled with 5-mm-thick layer of 8% Agar gel, and one healthy and clean pistachio leaf was cut to the size of the Petri dish diameter (52 mm) and the back of the leaf was placed on Agar gel in each Petri-dish, then placed into the plastic box (25 cm × 20 cm × 10 cm). A ventilation hole (0.2 mm and 3 cm diameter) was made in the middle of the lids of the Petri dish and box, respectively. Then it was covered by 50 mesh nets, and the relative humidity was controlled by placing saturated magnesium nitrate salt inside the box. The nymph and adult predators were fed on the nymphs of A. pistaciae, which were collected daily from the pistachio orchards.
Predation rate of A. minki pistaciae during immature stages
In order to determine the predation capacity of A. minki pistaciae during the nymphal stage, the food consumption of all nymphal instars was investigated in a pre-test separately. According to the results of the pre-test, the food consumption of the bugs was 50 CPPs (fourth instar nymphs). In the main test, newly emerged nymphs of 3 h-old A. minki pistaciae (first instar nymphs) were released individually on a Leaf-disk, and each individual was provided by 50 CPPs (fourth instar nymphs). Leaf-disks were checked daily, the number of consumed and alive psyllids was recorded, and the nymphs of the bug were moved to a new Leaf-disk containing nymphs of CPP. The experiments were continued for second, third, fourth, and fifth nymphal instars until the nymphs reached adult stage. Molting status, survival rate, and developmental durations of predator nymphs (the five nymphal instars) were recorded daily to determine the time spent in each nymphal stage.
In order to determine the total amount of consumed prey, this experiment was carried out with 15 replications, and the amount of consumed prey was recorded daily from the first nymphal instar to the adult stage of this predator. These experiments were performed at three constant temperatures (17, 26, and 30 ± 2 °C), relative humidity (55 ± 5%), and photoperiods of 16L:8D.
Predation rate of A. minki pistaciae during adult stage
After the adult emergence, the male and female individuals aged less than 1 day (0–24 h-old) were allowed to mate and then transferred to experimental Leaf-disks as described earlier. According to the results of the pre-test, the food consumption of adults in each Petri dish was estimated to be 200 CPPs (100 nymphs of the fourth nymphal stage of CPP for each bug) before the main experiment. The number of the consumed psylla and the laid eggs were counted daily until the death of adults; also, the survival rate and longevity of adults were calculated.
To determine the predation sex rate, the consumption rate of ten males was estimated under the same conditions, and to calculate the female daily consumption rate, the daily predation rate of males was subtracted from the average predation rate of the pairs. During the first week of the experiment, each dead male was replaced by an alive individual (Farhadi et al. 2011).
Evaluation of predation rate
In the age-stage, two-sex life table (Chi and Liu 1985), the age-specific survival rate (lx), and the age-specific fecundity (mx) for an individual of age x are calculated as:
$$ lx=\sum \limits_{j=1}^{\beta }{s}_{xj} $$
$$ {m}_x=\frac{\sum \limits_{j=1}^{\beta }{s}_{xj}{f}_{xj}}{\sum \limits_{j=1}^{\beta }{s}_{xj}} $$
where β is the number of life stages. The age-stage-specific survival rate (sxj) is the probability that a neonate survives to age x and stage j, and the age-stage-specific fecundity (fxj) means the mean number of offspring produced by individual A. minki pistaciae of age x and stage j per day.
The age-specific predation rate (kx) is the mean number of the fourth nymphal instar of A. pistaciae consumed by A. minki pistaciae at age x:
$$ {k}_x=\frac{\sum \limits_{j=1}^{\beta }{s}_{xj}{c}_{xj}}{\sum \limits_{j=1}^{\beta }{s}_{xj}} $$
By using sxj, the age-stage-specific net consumption rate (qx) gives the weighted number of A. pistaciae consumed by A. minki pistaciae of age x and is calculated as:
The net consumption rate (C0) is the total amount of A. pistaciae consumed by an average individual during its longevity. This parameter shows the predation capacity of a predator population (both sexes and all individuals that died before the adult stage), where δ is the last age of the population:
$$ {C}_0=\sum \limits_{x=0}^{\partial }{q}_x=\sum \limits_{x=0}^{\partial }{k}_x{l}_x=\sum \limits_{x=0}^{\partial}\sum \limits_{j=1}^{\beta }{s}_{xj}{c}_{xj} $$
The transformation rate from food mass to pest offspring (Qp) is the ratio of the net consumption rate to the net reproductive rate (R0). Qp gives the quantity of food needed for the production of an offspring and is calculated as:
$$ {Q}_p=\frac{C_0}{R_0} $$
The age-stage-specific consumption rate (cxj) surveys the differentiation of stage and the variable predation rate among individuals. This item gives the average amount of A. pistaciae consumed by an individual of A. minki pistaciae of age x and stage j (Chi and Yang 2003).
Data analysis
The daily predation rate of 15 individuals was analyzed according to Chi and Yang (2003) by the age-stage, two-sex consumption rate, MS Chart software (Chi 2017) (Ver. 2017.05.28). The standard errors of the consumption parameters were also calculated, using both the bootstrap method (n = 10,000) and Tukey’s test (0.05); also, the figures were drawn with Sigma Plot (Ver. 13.0, Systat software Inc.).