these two methods seem negligible, still, because of the unrealistic assumptions of
traditional life table analysing method, the estimated outputs are unreliable. Another
deficiency of conducted studies is the small cohort size, which is so small that it
might produce an incorrect estimation of population parameters.
2.5 Predator-Prey Dynamics
2.5.1 Functional Response of Most Important Coccinellid
Species to Different Prey Types
The functional response (F.R.) assessment is one of the most commonly used criteria
evaluating predator efficiency. This is a quantitative description of a predator’s
ability to consume prey. Although Solomon (1949) introduced it initially, Holling
(1959) developed the concept in details and described quantitative methods for
measuring the functional response. It describes the relation of predation with
increasing prey densities. Basically, there are three types of functional response to
initial prey densities, the linear (type I), the curvilinear (type II) and the sigmoidal
(type III). The output parameters of functional response experiments are search rate
and handling time. Instantaneous search rate (or attack constant) is a function of
encounter rate between predator and prey. It could be defined as the extent of area
covered in a time unit by a predator (Holling 1961; Rogers 1972). Handling time is
the amount of time spent on non-searching activities (subduing, killing, eating a
prey and resting) (Juliano 2001). The type of functional response and values of
related parameters of different species of lady beetles, especially variegated lady
beetle, Hippodamia variegata towards different prey species has been addressed in
Iranian studies extensively (Table 2.3).
One of the earliest functional response studies of variegated lady beetle done in
Iran dates back to Jafari and Goldasteh (2009) who reported the functional response
of H. variegata females and males to different densities of black bean aphid. Farhadi
et al. (2010) considered the functional response of all life stages of H. variegata on
the same aphid species Aphis fabae. Both researchers reported a type II functional
response for H. vareigata. In spite of the shared prey type and similar equation used
for analysis, their results were very different (Table 2.3). They reported type II
response for all life stages, however, searching efficiency of females was more than
100 times higher than that reported by Jafari and Goldasteh (2009) although, the
handling time showed lesser difference (two times). Based on their results, males and
secondly, the fourth instar larvae have the highest searching efficiency among life
stages and the females and fourth instar larvae showed the shortest handling time.
Therefore, it seems that females are the most voracious stage. This has been
confirmed by Madadi et al. (2011), who reported the fourth instar larvae has the
lowest handling time compared to other stages tested in their study on the effects of
prey types and experimental set-ups on the functional response type of H. variegata.
58
H. Madadi
traditional life table analysing method, the estimated outputs are unreliable. Another
deficiency of conducted studies is the small cohort size, which is so small that it
might produce an incorrect estimation of population parameters.
2.5 Predator-Prey Dynamics
2.5.1 Functional Response of Most Important Coccinellid
Species to Different Prey Types
The functional response (F.R.) assessment is one of the most commonly used criteria
evaluating predator efficiency. This is a quantitative description of a predator’s
ability to consume prey. Although Solomon (1949) introduced it initially, Holling
(1959) developed the concept in details and described quantitative methods for
measuring the functional response. It describes the relation of predation with
increasing prey densities. Basically, there are three types of functional response to
initial prey densities, the linear (type I), the curvilinear (type II) and the sigmoidal
(type III). The output parameters of functional response experiments are search rate
and handling time. Instantaneous search rate (or attack constant) is a function of
encounter rate between predator and prey. It could be defined as the extent of area
covered in a time unit by a predator (Holling 1961; Rogers 1972). Handling time is
the amount of time spent on non-searching activities (subduing, killing, eating a
prey and resting) (Juliano 2001). The type of functional response and values of
related parameters of different species of lady beetles, especially variegated lady
beetle, Hippodamia variegata towards different prey species has been addressed in
Iranian studies extensively (Table 2.3).
One of the earliest functional response studies of variegated lady beetle done in
Iran dates back to Jafari and Goldasteh (2009) who reported the functional response
of H. variegata females and males to different densities of black bean aphid. Farhadi
et al. (2010) considered the functional response of all life stages of H. variegata on
the same aphid species Aphis fabae. Both researchers reported a type II functional
response for H. vareigata. In spite of the shared prey type and similar equation used
for analysis, their results were very different (Table 2.3). They reported type II
response for all life stages, however, searching efficiency of females was more than
100 times higher than that reported by Jafari and Goldasteh (2009) although, the
handling time showed lesser difference (two times). Based on their results, males and
secondly, the fourth instar larvae have the highest searching efficiency among life
stages and the females and fourth instar larvae showed the shortest handling time.
Therefore, it seems that females are the most voracious stage. This has been
confirmed by Madadi et al. (2011), who reported the fourth instar larvae has the
lowest handling time compared to other stages tested in their study on the effects of
prey types and experimental set-ups on the functional response type of H. variegata.
58
H. Madadi