Longevity of T. evanescens differed distinctly among individuals provided with different food supplements (F = 12.08, df = 16,238, Fig. 1a). Only P, Rj, and Pg + P that failed to increase the longevity over the control. The other 14 diets significantly increased longevity, whereas H + Rj and H + P were the best diets that prolonged the longevity to 12.2 ± 1.3 and 9.9 ± 1.2 days than 3.2 ± 0.5 days for control. T. bourarachae showed also significant differences in average longevity, when provided with different food supplements (F = 14.8, df = 16,238, Fig. 1b). Nine diets (H + Rj + P, H, H + Pg + P, H + Rj, H + Pg + Rj, H + Pg + Rj + P, H + Pg, H + P, and Rj + P) prolonged significantly the longevity, whereas H + Rj + P and H caused the longest life time (11.6 ± 0.87 and 11.5 ± 0.45 days), while the unfed females lived only for (5.2 ± 0.38 days). Females fed on the remaining eight diets did not show any increase in longevity relative to the unfed control. Longevity of T. cacoeciae varied also significantly among females provided with different food supplements (F = 22.6, df = 16,238, Fig. 1b). All eight diets, contained honey and sugar solution improved the female’s longevity. The best ones were H + Rj and H that prolonged the longevity to (9.9 ± 0.9 and 9.6 ± 1.1 days) than (1.5 ± 0.13 days) in the control. The other diets did not improve longevity.
Feeding on carbohydrates can enhance adult parasitoid longevity (Gómez et al. (2012). Obtained results showed that honey as a source of carbohydrates had the main effect for improving the longevity of the three Trichogramma species, when a very small amount of royal jelly was added to it. In the case of T. evanescens and T. bourarachae, longevity increased with a factor ranged between (1.8 and 3.08, and 1.8 and 2.2), respectively. T. cacoeciae showed the highest improvement, with a factor of (1.9–6.4). These findings are in consistent with other researches related to the other species, i.e., T. brassicae, when its longevity increased about 5-folds by feeding on honey (Malati and Hatami 2010). T. euproctidis females lived for 10.5 days when fed on honey, while lived 2.6 days in case of feeding on water alone (Tunçbilek et al. 2012). Also, Özder and Demirtas 2017 recorded that T. brassicae females which fed on honey, honey + acacia nectar, honey + apple syrup lived significantly longer than those females that fed on other floral nectars and artificial diets.
The fecundity of T. evanescens varied significantly among different diet treatments (F = 8.5, df = 16,238, Fig. 2a). All diets improved the fecundity (especially those containing honey), except Rj, Rj + P, and P that were similar or below the control. H + Rj + P (119.3 ± 12.16 egg), H + Rj (118.87 ± 12.86 egg), H (116.87 ± 9.7 egg), and H + Pg + Rj (115.27 ± 15.6 egg) gave the highest numbers of parasitized eggs compared to 57.87 ± 10.7 egg in the control. The fecundity of T. bourarachae also differed significantly among different diet treatments (F = 9.7, df = 16,238, Fig. 2b). The fecundity of individuals fed on Pg, H + Pg, Pg + Rj, Rj, Pg + P, and P was similar or even lower than the control. The remaining 11 diets tested improved the fecundity significantly, the female fed on H + Rj + P, H + Pg + p, and H + Pg + Rj + P laid the highest numbers of eggs (95.5 ± 6.67, 92.4 ± 7.7, and 86.0 ± 8.65) compared with (47.8 ± 4.3) eggs for unfed wasps. The fecundity of T. cacoeciae differed distinctly among different diets treatments (F = 15.06, df = 16,238, Fig. 2c). All diets contained honey and sugar solution improved the fecundity, but other diets had insignificant effects. H + Rj and H were the best diets that affected significantly and raised the fecundity to (64.3 ± 7.1 and 54.0 ± 6.5) eggs than (13.1 ± 1.61) eggs in the control.
Adults of different Trichogramma spp., like most parasitoid species, are fed naturally upon nectar, pollen as recorded by Wellinga and Wysoki (1989), and honeydew (Koptur 1992). In the laboratory, natural food sources are commonly replaced by honey or sugar. Obtained results showed that honey had the main effect on fecundity of all species, but this efficacy was improved in some cases, when pollen grains were added, propolis, and especially royal jelly (propolis and royal jelly gave a positive effect when added in a small amount to honey, but they had a harmful effect when it was used alone or in a big amount). This improvement appeared significantly in case of T. cacoeciae with H + Rj diet, which increased fecundity with a factor of (4.4) more than the control. This may probably due to the special food royal jelly, which responsible of the development of honeybee larvae in to queen bees as stated by Brouwers et al. (1987).
In T. bourarachae, fecundity was improved when Pg + Rj + P, Pg + P, and Rj + P were added to honey with a factor ranging (1.8–2.03). Obtained results are consistent with those reported by Malati and Hatami (2010) who stated that fecundity of honey-fed T. brassicae adults increased approximately 4-folds than the unfed females. Similar results were recorded for the same Trichogramma species by Özder and Demirtas (2017) that the fecundity was significantly greater when the wasps were fed on honey (106.8 ± 30.26 eggs), honey + acacia nectar (105.4 ± 12.26 eggs), and honey + Paulownia nectar (103.13 ± 15.34 eggs), than royal jelly + red tulip nectar (3.33 ± 1.34 eggs). In addition, Zhang et al. (2004) recorded that feeding on corn pollen increased the offspring production of T. brassicae females than the unfed ones, but it was lower than those fed on honey or pollen grains + honey. Paraiso et al. (2012) recommended feeding Trichogramma females on honey in mass-rearing programs to raise a sustainable population of T. fuentesi in the laboratory. Obtained results also are in conformity with the work of Siam et al. (2014) who reported the highest fecundity of T. evanescens females by feeding on pure sugarcane honey (58.2 ± 2.5 eggs), followed by pure bee honey (52.8 ± 2.1 eggs). Availability of honey as food supplement also increased the parasitization rate of T. cacoeciae as recorded by Mansour (2019). For the three Trichogramma species, fecundity was positively correlated to longevity, with T. cacoeciae benefitting much more from the increase in longevity, followed by T. evanescens then T. bourarachae (Fig. 3).
There were insignificant differences in emergence rate of T. evanescens females, when fed on different diets, despite the differences in averages (F = 0.752, df = 16,238, Fig. 4a). The emergence rate in T. bourarachae differed significantly among the different diets (F = 2.00, df = 16,238, Fig. 4b). Most of the diets did not affect the emergence rate, except Rj + P, Pg + Rj, and H + P, which decreased the emergence rate to (86.87 ± 1.58, 89.26 ± 2.58, and 89.16 ± 1.6%) than (91.90 ± 2.07%) in the control. In the case of T. cacoeciae, there were significant differences in emergence rates too (F = 2.37, df = 16,238, Fig. 4c). The greatest rate was recorded at Pg + P and Rj + P (99.2 ± 0.2%). The lowest rate was obtained by the sugar solution, which was 94.2 ± 1.5 %.
Obtained results showed that there were insignificant differences in the emergence rate of T. evanescens at different treatments. This result was similar to the findings of Zhang et al. (2004) and Malati and Hatami (2010) on T. brassicae and Fuchsberg et al. (2007) on T. ostriniae, who reported that no effect of feeding treatments on progeny emergence rate. In the case of T. bourarachae and T. cacoeciae, significant effects on emergence rate were found. This result agrees with that of Tunçbilek et al. (2012), who reported a significant influence of diets on T. euproctidis adult emergence.
The sex ratio of T. evanescens varied significantly among different diet treatments (F = 6.6, df = 16,238, Fig. 5a). The highest percentage of females emergence obtained by feeding on Pg (76.48 ± 3), Pg + P (74.53 ± 3.6), control (74.5 ± 3.5), and H + Rj (68.79 ± 2.4). The remaining diets decreased the percentage of females, especially H + P, which decreased the percentage to (45.5 ± 4.09). The sex ratio of T. bourarachae also differed significantly among different diet treatments (F = 2.5, df = 16,238, Fig. 5b). H + Pg + P, H + Rj + P, and H decreased the female percentage to (67.18 ± 3.9, 68.03 ± 2.97, and 68.17 ± 3.22) than the control (80.19 ± 2.26). T. cacoeciae is a thelytokus type, all progeny are females, therefore, it was not affected by different diets (Fig. 5c).
Progeny of long-lived females of Trichogramma species are male biased as confirmed by Malati and Hatami (2010). In these results, long-lived females of T. evanescens and T. bourarachae had lower female offspring percentages, except when T. evanescens was fed on H + Rj, which caused the longest lifetime, higher fecundity and did not decrease female percentage. When T. bourarachae was fed on H + Rj and H + Pg + Rj, it lived a longer time, but did not decrease the female percentage. This was probably due to royal jelly. Lower proportion of female progeny in case of some of the supplemental diets, which caused a long living, does not mean that adult nutrition decreases parasitoid potential. In fact, the total number of female progeny per fed female was significantly more than the unfed ones. Therefore, it should be considered that adult nutrition is not omitted because of lower proportion of female progeny. Higher fecundity in fed parasitoid can compensate for this limitation.