Population dynamics of the phytophagous lady beetle, Epilachna vigintioctopunctata, in an eggplant field in Sumatra

Abstract

SummaryFrom December, 1981 to December 1982, the population dynamics of the phytophagous lady beetle Epilachna vigintioctopunctata (Fabricius) (Evp) was studied by mark‐recapture of adults and the construction of a life table in an eggplant field in Padang, Sumatra, Indonesia. After planting of the host plants, adults of Evp soon colonized and oviposited massively, resulting in a rapid population growth for 1–2 months; thereafter, the population increase slowed due to defoliation. Three–four months thereafter the host plants recovered their leaves, but leaf quality was less suitable for Evp and, as a result, the population remained at a low level during the rest of the study period. Adult population size fluctuated 7–8 fold during the study period. Adult Evp showed a 1∶1 sex ratio. The daily rate of residence, ψi, derived by theJolly‐Seber formula fluctuated from 0.9 to 1.0. The estimated mean length of residence of adults was 16.5 days (male) and 15.2 (female), but this was probably much shorter than the actual longevity, because the adults were so active that they flew away or dropped off the plants when they were approached or were slightly disturbed. Adults showed a rich variation in elytral spot patterns. The average number of non‐persistent spots per elytron was 0.52 in males and 1.08 in females; 23.3% of males and 24.6% of females had confluence(s). The life table shows that parasitism by wasps, which killed 9.7% of eggs and 35.0% of pupae, and starvation by overcrowding contributed most to the total mortality from egg to adult emergence (>98%). The high dispersal power of adults, coupled with their prolonged lx−mx schedules was advantageous for exploiting food plants which were variable in space and time.

Natural Enemies of Ladybird Beetles

“…In the last part of the chapter we discuss the role of natural enemies in infl uencing numerical changes in Depletion of food resources due to feeding of epilachnine larvae is often reported in the tropics (Abbas & Nakamura 1985, Nakamura et al 1988, Inoue et al 1993 ), but also in temperate regions (Nakamura 1976, Kimura & Katakura 1986, indicating inability of natural enemies to regulate herbivore populations in a density -dependent manner. However, in temperate latitudes of the Russian Far East (44 ° N), Kovalenko and Kuznetsov ( 2005 ) found good synchronization between population dynamics of H. vigintioctomaculata and its parasitoid, N. afi ss ae, hinting at a density -dependent regulatory mechanism.…”

“…Some of these studies were performed in the tropical regions of Sumatra (Indonesia) (latitude 1 ° S) (Abbas & Nakamura 1985, Nakamura et al 1988, Inoue et al 1993 and Ethiopia (7 ° N) (Beyene et al 2007 ), and others from the temperate Japanese islands Honshu (35 -36 ° N) (Nakamura 1976, Nakamura & Ohgushi 1981, Shirai 1987 and Hokkaido (43 ° N) (Kimura & Katakura 1986 ). The most striking difference between the mortality factors affecting tropical and temperate epilachnines concerns parasitoids.…”

Abundance of insect seed predators and intensity of seed predation on Shorea (Dipterocarpaceae) in two consecutive masting events in Peninsular Malaysia

“…Population size in insects fluctuates not only by resource limitation but also because of seasonality (Kato et al 2000), stochastic environmental changes (e.g. drought; Kishimoto-Yamada et al 2009), the abundance of natural enemies (Nakamura et al 1988) and other unknown factors (Wolda 1992), even in aseasonal tropical habitats. Therefore, we need to interpret our results carefully and consider the biological and environmental information available.…”

Population Dynamics of an Isolated Population of the Tropical Pyrrhocorid Bug, Melamphaus faber, Feeding on Seeds of Hydnocarpus Trees and the Specialist Predator, Raxa nishidai in Bogor, West Java, Indonesia.

“…Detailed population analysis based on life-table construction is necessary to identify factors involved in population fluctuations quantitatively and in particular to examine the effect of natural enemies (Bellows et al, 1992;Nakamura et al, 1990). Nakamura and his colleagues have carried out detailed population studies on a phytophagous ladybird beetle (Nakamura et al, 1988;1990), using the mark-recapture method in Padang, West Sumatra, climate of which is warm and rainy all the year round. According to Nakamura et al (1988Nakamura et al ( , 1990 distinct generations (on average 8 generations a year) were evident particularly in the egg stage, though some degree of overlap in adult generations also existed.…”

“…Nakamura and his colleagues have carried out detailed population studies on a phytophagous ladybird beetle (Nakamura et al, 1988;1990), using the mark-recapture method in Padang, West Sumatra, climate of which is warm and rainy all the year round. According to Nakamura et al (1988Nakamura et al ( , 1990 distinct generations (on average 8 generations a year) were evident particularly in the egg stage, though some degree of overlap in adult generations also existed. They also showed that a 48-day cycle of rainfall was clearly recognized by power spectral analysis (Nakamura et al, 1990), and consequently suggested that the rainfall cycle had a relevance to shoot growth of host plants, which in turn accelerate the oviposition activities, at least to some extent.…”