Effect of mating and previous parasitism on functional response of Trissolcus djadetshkoe (Hym.: Scelionidae) an egg parasitoid of Eurygaster integriceps (Hem.: Scutelleridae)

Trissolcus djadetshkoe Rjachowsky (Hym.: Scelionidae) is an egg parasitoid of sunn pest Eurygaster integriceps Puton (Hem.: Scutelleridae) in Iran. Searching efficiency of this species was determined in a functional response context. Effect of female insemination as well as parasitism experience was also investigated. Host densities of 2, 4, 7, 14, 28 and 56 eggs were offered to a single female in 20, 20, 15, 15, 10 and 10 replications in a 24 h experiment in 1.5×10 cm vials. Virgin vs. inseminated females as well as inexperienced vs. experienced ones were used in two sets of experiments. All experiments were conducted in a growth chamber (26±1 ºC, 50±10% RH, 16: 8 h photoperiod). Logistic regression and nonlinear regression model of random search were used for analysis. All parasitoid responses were type III. Experienced females showed lower parasitism in all densities. Maximum attack rate estimates were 14 in experienced females vs. 34 in inexperienced ones. It seems that previous reproductive efforts have depleted energy of the females. A lighter difference was observed in virgin females over inseminated ones (25 vs. 17). This difference probably concerns with costs of sex allocation for inseminated mothers.