Abstract. Body size is a standard criterion of quality control in insect rearing and often assumed to correlate with fitness in parasitoid wasps, but various metrics of body size can be used. The purpose of this study was to determine which morphological feature provides the best correlation with body size and egg load in a thelytokous population of the parasitoid wasp, Lysiphlebus fabarum (Marshall), when reared on Aphis fabae Scopoli under standardized conditions in a growth chamber (21 ± 1°C, 60-70% RH, and 16L : 8D). Candidate metrics included head width, length and width of the pronotum, length and width of the right forewing, and length of the right hind tibia. In the first experiment, correlations were determined between these measurements and overall wasp body length. As head width and hind tibia length emerged as the most suitable proxies for total body length, the next experiment these two variables as proxies for egg load in females reared from different nymphal instars of the host aphid. There was a non-linear relationship between body size and egg load of wasps emerging from hosts parasitized in different nymphal instars. Egg load increased linearly with body size across all host growth stages, but the second nymphal instar was the most suitable stage for parasitism when speed of development was factored in. The results suggest that head width is a suitable morphometric for monitoring quality control in mass-reared cultures of this wasp.

In Iran, Lysiphlebus fabarum (Marshall) (Hymenoptera: Braconidae: Aphidiinae) is a uniparental parasitoid of the black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae), that possesses various highly evolved adaptations for foraging within ant-tended aphid colonies. Direct observations and video recordings were used to analyze the behavior of individual females foraging for A. fabae on bean leaf disks in open arenas in the laboratory. Females exploited aphids as hosts and as a source of food, allocating within-patch time as follows: resting - 10.4%, grooming - 8.2%, searching - 11.5%, antennation (host recognition) - 7.5%, antennation (honeydew solicitation mimicking ants) - 31.9%, abdominal bending (attack preparation) 19.7%, probing with the ovipositor (attack) - 10.8%. The mean handling time for each aphid encountered was 2.0 ± 0.5 min. Females encountered an average of 47.4 ± 6.4 aphids per hour, but laid only 1.2 eggs per hour. The ovipositor insertion time for parasitism ranged from 2 sec to longer than a minute, but most insertions did not result in an egg being laid. A. fabae defensive behaviors included kicking, raising and swiveling the body, and attempts to smear the attacker with cornicle secretions, sometimes with lethal results. Food deprivation for 4–6 h prior to testing increased the frequency of ant mimcry by L. fabarum. Females also used ant-like antennation to reduce A. fabae defensive behavior, e.g. the frequency of kicking. L. fabarum attacks primed A. fabae to be more responsive to subsequent honeydew solicitation, such that experienced females improved their feeding success by alternating between the roles of parasitoid and ant mimic. These results reveal the possibility for mutualisms to evolve between L. fabarum and the ant species that tend A. fabae, since L. fabarum receive ant protection for their progeny and may benefit the ants by improving A. fabae responsiveness to honeydew solicitation.

This study tested effects of maternal body size on foraging behavior and progeny development in a thelytokous population of Lysiphlebus fabarum (Marshall) (Hymenoptera: Braconidae). Small and large wasps were reared from first and second instar hosts [black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae)], respectively, and each was provided with a patch (bean leaf disk) containing either 15 small (second instar) or 15 large (fourth instar) hosts for a 30-min foraging period. Neither body size nor host size affected time allocation to various behaviors within a patch, but second instar aphids produced significantly more mummies than fourth instars. The preferred attack orientation was from the side of the aphid, suggesting wasps were sensitive to the risk of smearing with cornicle secretions. Few wasps developed in fourth instar hosts, suggesting later host instars were somewhat resistant to parasitism. Second instar hosts, the most suitable stage for L. fabarum development, relied more on defensive behavior, specifically kicking and secreting cornicle droplets. Large wasps were more likely to elicit a double cornicle secretion, indicating that aphids graded their response to the size of the attacker. Larger wasps were also more likely to be smeared with cornicle secretion, suggesting they were more vulnerable than small wasps. Although small wasps had smaller eggs than large wasps, there was no effect of maternal egg size on the size of progeny. However, daughters of small females emerged with larger egg loads than daughters of large mothers, and their eggs tended to be slightly smaller, although not significantly. Regression analysis revealed a positive correlation between maternal egg size and progeny developmental time for small and large wasps, and between maternal egg size and progeny egg load for small wasps. These results confirm maternal effects of body size in an aphid parasitoid, and reveal that vulnerability to host behavioral defenses is also body size dependent.

The noctuid Helicoverpa armigera is an economically important pest of agricultural crops in Iran and other countries. Research is evaluating the capacity of Trichogramma parasitoids to control H. armigera populations on field crops. The objective of this research was to determine if young rather than old H. armigera eggs were optimal for Trichogramma euproctidis development, reproduction, and life table parameters. Bioassays involved exposing T. euproctidis mated females to H. armigera 14, 38, or 62 h old eggs within 24 h in laboratory arenas. Results indicated that the number of host eggs parasitized successfully by T. euproctidis decreased as host egg age increased. Host egg age had no significant effect on T. euproctidis adult emergence. Adults that developed in 14 h old eggs had greater longevity and fecundity than those that developed in 38 h or 62 h old eggs. The intrinsic rate of increase (r) was greatest, and the mean generation time (T) was lowest for T. euproctidis reared in 14 h old eggs. This study indicates that young H. armigera eggs are more suitable than old ones for T. euproctidis development and reproduction. This study is important because it provides evidence, for the first time, that T. euproctidis can utilize H. armigera as a rearing host. Using young rather than old host eggs could ensure the persistence of a T. euproctidis mass production system to support augmentative releases.

Potential of Orius albidipennis Reuter as a biological control agent of tomato leaf miner (Tuta absoluta Meyrick) eggs was evaluated and comparing by estimating its functional response on the two tomato cultivars with different physical characteristics under laboratory conditions. Eight prey densities (8, 10, 15, 20, 25, 30, 35, and 40 eggs per leaf disc) were exposed to female adult of the predator during 24-h period for each tested cultivar under controlled conditions of 26 ± 2°C, 60 ± 5% RH and 16:8 h (L:D). Our results revealed that adult females of the predatory bug exhibited type III functional responses to different the densities of prey on both cultivars. The attack rate of the predator on trichome dense cultivar Fillous ® was significantly lower than trichome non-dense cultivar Cherry ®. In addition, its handling time on Fillous ® was significantly higher than Cherry ® cultivar. Our study demonstrates that O. albidipennis can be a good potential candidate for the biological control of T. absoluta eggs in tomato fields and greenhouses. The predator efficacy in low dense trichome cultivars is significantly higher than that in high dense trichome cultivars. The results of the study can be used in integrated pest management programs of T. absoluta.