2.6 Population Fluctuations of Hippodamia variegata
and Other Lady Beetle Species
Insect populations like other organisms in response to different factors increase,
decline and oscillate profoundly. Clearly, different factors such as climatic factors,
competition, host quality and quantity, diseases, natural enemies and others might be
influential and arise or dampen insect populations. Population dynamics attempt to
find the causes of those fluctuations, their periods and strength. Although it seems
that many questions have not been answered yet. Undoubtedly, knowledge of
the population dynamics of aphids and their natural enemies leads us to a better
understanding of their associations and integrated pest management (Rakhshani
et al. 2009).
There are few studies that dealt with the population structure and fluctuation of
lady beetle in Iran. Usually, the population oscillations of aphids and lady beetle
have been presented across one or two consequent years. Sometimes, the relation of
different abiotic or biotic factors with prey and lady beetle populations has been
correlated. It has been expressed that H. variegata was an abundant species in central
plain of Iran and its population had two peaks yearly (May–July and early of
autumn) while the seven spotted lady beetle had just one dominant peak during
autumn (Rakhshani et al. 2009). The interesting point was that the lady beetle
population was positively correlated with aphid populations. This synchrony
increases the effectiveness of the lady beetle to suppress the aphid population.
Similarly, the main population peaks of these two lady beetles reached on May–
July and September in Alfalfa fields of Hamedan province (Soleimani and Madadi
2015; Tavoosi Ajvad et al. 2012). The H. variegata population varies significantly
with increasing temperatures, but unlike C. septempunctata, it was not correlated
with pea aphid population significantly. Farsi et al. (2010) reported the peak of
C. septempunctata in the middle of March following canola aphids rising in Ahvaz
(Southern Iran). Furthermore, Afshari et al. (2000) reported the highest density of
S. gilvifrons and Oligonychus sacchari McGregor, 1942 in late July and their
populations were positively correlated. This species emerged on sugarcane in early
summer and overwintered as an adult out of the sugarcane fields (Narrei et al. 2005).
2.7 Intraguild Predation Studies
Intraguild predation or predatory interference is a relatively new field in insect
ecology. This term was coined by Polis et al. (1989) firstly and afterward became
prevalent quickly. By definition, intraguild predation (IGP) is a combination of
predation and competition, i.e. two or more competitors that compete for a shared
prey involved in predation. In this interaction, one of the competitors is superior and
named IG or top predator while, other is inferior, called IG prey. The shared
herbivore prey often is extraguild prey (EXG). The outcome of IGP based on
72
H. Madadi
and Other Lady Beetle Species
Insect populations like other organisms in response to different factors increase,
decline and oscillate profoundly. Clearly, different factors such as climatic factors,
competition, host quality and quantity, diseases, natural enemies and others might be
influential and arise or dampen insect populations. Population dynamics attempt to
find the causes of those fluctuations, their periods and strength. Although it seems
that many questions have not been answered yet. Undoubtedly, knowledge of
the population dynamics of aphids and their natural enemies leads us to a better
understanding of their associations and integrated pest management (Rakhshani
et al. 2009).
There are few studies that dealt with the population structure and fluctuation of
lady beetle in Iran. Usually, the population oscillations of aphids and lady beetle
have been presented across one or two consequent years. Sometimes, the relation of
different abiotic or biotic factors with prey and lady beetle populations has been
correlated. It has been expressed that H. variegata was an abundant species in central
plain of Iran and its population had two peaks yearly (May–July and early of
autumn) while the seven spotted lady beetle had just one dominant peak during
autumn (Rakhshani et al. 2009). The interesting point was that the lady beetle
population was positively correlated with aphid populations. This synchrony
increases the effectiveness of the lady beetle to suppress the aphid population.
Similarly, the main population peaks of these two lady beetles reached on May–
July and September in Alfalfa fields of Hamedan province (Soleimani and Madadi
2015; Tavoosi Ajvad et al. 2012). The H. variegata population varies significantly
with increasing temperatures, but unlike C. septempunctata, it was not correlated
with pea aphid population significantly. Farsi et al. (2010) reported the peak of
C. septempunctata in the middle of March following canola aphids rising in Ahvaz
(Southern Iran). Furthermore, Afshari et al. (2000) reported the highest density of
S. gilvifrons and Oligonychus sacchari McGregor, 1942 in late July and their
populations were positively correlated. This species emerged on sugarcane in early
summer and overwintered as an adult out of the sugarcane fields (Narrei et al. 2005).
2.7 Intraguild Predation Studies
Intraguild predation or predatory interference is a relatively new field in insect
ecology. This term was coined by Polis et al. (1989) firstly and afterward became
prevalent quickly. By definition, intraguild predation (IGP) is a combination of
predation and competition, i.e. two or more competitors that compete for a shared
prey involved in predation. In this interaction, one of the competitors is superior and
named IG or top predator while, other is inferior, called IG prey. The shared
herbivore prey often is extraguild prey (EXG). The outcome of IGP based on
72
H. Madadi