competitors of the same species or relative or homologue species that are foraging
simultaneously. Hence, the presence of choice among patches of different densities
as well as competitors is near to what occurs in nature. In a multi-patch experiment,
Iranipour et al. (2020) released 1–16 T. vassilievi females into an arena with five
patches of 1 to 15 egg clutches (14 eggs/clutch). They observed that one-clutch patch
was avoided by a single wasp, while other patches were visited equally. The
motivation threshold was concluded to be two clutches i. e. 28 eggs. In no-choice
experiments however, the wasp handled majority of eggs in tubes containing 4–28
eggs. This may suggest that the parasitoid can avoid poorer patches when it accesses
better ones. However, their results also revealed that the parasitoid seldom leaves a
poorer patch of its first choice. This led to lower exploitation in some cases in the
experimental arena. Although such behaviour may seem maladaptive in the experimental arena, it may be adaptive in a natural situation with scarce host and high risk
of leaving a worse situation hoping to find a better one. As soon as they added
number of foraging females within an arena, the restlessness of the parasitoids
increased. They left their situations repeatedly and even one-clutch patch also was
visited. This is due to interference between them. Time allocation to different
patches, however, was not equal. Both parasitism and time spent increased from
1 to 8 clutch patches, but then decreased at the highest density of 15 clutches. This
may be due to kairomone saturation and therefore habituation and confusion of the
parasitoid around the highest host density. The high correlation between patch-time
and parasitism suggests unimportance of interference because aggregation of wasps
in a patch did not lead to lower exploitation. Nevertheless, a significant negative
correlation was observed between searching efficiency and parasitoid density. This
may suggest the presence of mutual interference that divided into two components of
actual interference and pseudo-interference. The latter component was more important than the former one. Pseudo-interference arises from aggregation in some
patches (often denser ones) and avoiding the others that final result will be lower
exploitation. Therefore, parasitoid’s fidelity to a discovered patch benefits its host. In
this case, per capita parasitism declined as the number of foraging wasps increased
from 1 to 16 by a rate of 0.4. Inundation may be a solution. Results also showed that
the parasitoid responds to the presence of other individuals by accelerating its
handling and more efficient utilization of time. The total response (functional plus
numerical) of the parasitoid was type III and parasitism rate reached a maximum at
28 eggs. A similar study by Amir-Maafi (2000) had somewhat similar results by a
larger slope of decrease (coefficient m of Hassell and Varley, 1969) in searching
efficiency by wasp density (0.37 compared with 0.18–0.24). Iranipour et al. (2018a)
studied reaction of two species of T. vassilievi and T. grandis to each other and to
presence of conspecifics in a multipatch environment. Densities of 1, 8 and 16 parasitoids of single species with combinations of the same number of two species
(either 4 vassilievi + 4 grandis or 8 vassilievi + 8 grandis) were released on the same
arrange of host clutches. Results revealed that competition among T. grandis females
was more burdensome as it caused a strong decline in searching rate. Effect of
T. vassilievi females on conspecifics was moderate, but interspecific confrontation of
the two species had interesting results. T. grandis reduced intra-specific interference
8 Superfamily Platygastroidea: Natural Enemies of True Bugs, Moths, Other. . .
321
simultaneously. Hence, the presence of choice among patches of different densities
as well as competitors is near to what occurs in nature. In a multi-patch experiment,
Iranipour et al. (2020) released 1–16 T. vassilievi females into an arena with five
patches of 1 to 15 egg clutches (14 eggs/clutch). They observed that one-clutch patch
was avoided by a single wasp, while other patches were visited equally. The
motivation threshold was concluded to be two clutches i. e. 28 eggs. In no-choice
experiments however, the wasp handled majority of eggs in tubes containing 4–28
eggs. This may suggest that the parasitoid can avoid poorer patches when it accesses
better ones. However, their results also revealed that the parasitoid seldom leaves a
poorer patch of its first choice. This led to lower exploitation in some cases in the
experimental arena. Although such behaviour may seem maladaptive in the experimental arena, it may be adaptive in a natural situation with scarce host and high risk
of leaving a worse situation hoping to find a better one. As soon as they added
number of foraging females within an arena, the restlessness of the parasitoids
increased. They left their situations repeatedly and even one-clutch patch also was
visited. This is due to interference between them. Time allocation to different
patches, however, was not equal. Both parasitism and time spent increased from
1 to 8 clutch patches, but then decreased at the highest density of 15 clutches. This
may be due to kairomone saturation and therefore habituation and confusion of the
parasitoid around the highest host density. The high correlation between patch-time
and parasitism suggests unimportance of interference because aggregation of wasps
in a patch did not lead to lower exploitation. Nevertheless, a significant negative
correlation was observed between searching efficiency and parasitoid density. This
may suggest the presence of mutual interference that divided into two components of
actual interference and pseudo-interference. The latter component was more important than the former one. Pseudo-interference arises from aggregation in some
patches (often denser ones) and avoiding the others that final result will be lower
exploitation. Therefore, parasitoid’s fidelity to a discovered patch benefits its host. In
this case, per capita parasitism declined as the number of foraging wasps increased
from 1 to 16 by a rate of 0.4. Inundation may be a solution. Results also showed that
the parasitoid responds to the presence of other individuals by accelerating its
handling and more efficient utilization of time. The total response (functional plus
numerical) of the parasitoid was type III and parasitism rate reached a maximum at
28 eggs. A similar study by Amir-Maafi (2000) had somewhat similar results by a
larger slope of decrease (coefficient m of Hassell and Varley, 1969) in searching
efficiency by wasp density (0.37 compared with 0.18–0.24). Iranipour et al. (2018a)
studied reaction of two species of T. vassilievi and T. grandis to each other and to
presence of conspecifics in a multipatch environment. Densities of 1, 8 and 16 parasitoids of single species with combinations of the same number of two species
(either 4 vassilievi + 4 grandis or 8 vassilievi + 8 grandis) were released on the same
arrange of host clutches. Results revealed that competition among T. grandis females
was more burdensome as it caused a strong decline in searching rate. Effect of
T. vassilievi females on conspecifics was moderate, but interspecific confrontation of
the two species had interesting results. T. grandis reduced intra-specific interference
8 Superfamily Platygastroidea: Natural Enemies of True Bugs, Moths, Other. . .
321