Ecology and Biodiversity of Agriculturally Important Rice Field Arthropods
ECOLOGY AND BIODIVERSITY OF AGRICULTURALLY
IMPORTANT RICE FIELD ARTHROPODS
J. Diraviam
P. G. and Research Department of Zoology
Loyola College
Chennai - 600 034
Studies on the ecology and biodiversity of arthropods which are agriculturally important were undertaken from January 2002 to December 2003 in five seasons in 13 farmers’ rice fields in the districts of Kancheepuram, Tiruvallur, Vellore and Villupuram of the north-eastern zone of Tamil Nadu State, India.
Most of the studies were confined to Kovur village of Kancheepuram district, where rice is raised in three seasons, viz., Navarai (January-April), Sornavari (April - August) and Samba (August - December). The field in which the study was undertaken was not applied with pesticides for over six years.
In the other locations, at least one season study was made in Vallam in Kancheepuram district and Budur in Tiruvallur district. In the remaining ten locations the observations were made as roving surveys (1 to 3 observations).
1. SPECIES COMPOSITION
The study on species composition conducted by (i) visual observation, (ii) net sweep collection and (iii) hand collection brought out the presence of 314 taxa of insects under 110 families and 15 orders, 61 taxa of spiders under 16 families, and 5 taxa of mites under 3 suborders and 5 families, in the rice nurseries / main fields in all the locations surveyed. They included herbivores, entomophages and neutrals, and were identified upto the lowest taxa possible.
2. BIODIVERSITY INDICES
The three richness indices, viz., Hill’s number (N0), Margalef index (R1), Menhinick index (R2), four diversity indices viz., Simpson’s index (λ), Shannon’s index (H’), Hill’s diversity No. 1 (N1), Hill’s diversity No. 2 (N2) and five evenness indices (E1 to E5) were used for quantification of arthropod biodiversity in different rice ecosystems during different seasons. Rarefaction method was adopted for working out the expected number of
IMPORTANT RICE FIELD ARTHROPODS
J. Diraviam
P. G. and Research Department of Zoology
Loyola College
Chennai - 600 034
Studies on the ecology and biodiversity of arthropods which are agriculturally important were undertaken from January 2002 to December 2003 in five seasons in 13 farmers’ rice fields in the districts of Kancheepuram, Tiruvallur, Vellore and Villupuram of the north-eastern zone of Tamil Nadu State, India.
Most of the studies were confined to Kovur village of Kancheepuram district, where rice is raised in three seasons, viz., Navarai (January-April), Sornavari (April - August) and Samba (August - December). The field in which the study was undertaken was not applied with pesticides for over six years.
In the other locations, at least one season study was made in Vallam in Kancheepuram district and Budur in Tiruvallur district. In the remaining ten locations the observations were made as roving surveys (1 to 3 observations).
1. SPECIES COMPOSITION
The study on species composition conducted by (i) visual observation, (ii) net sweep collection and (iii) hand collection brought out the presence of 314 taxa of insects under 110 families and 15 orders, 61 taxa of spiders under 16 families, and 5 taxa of mites under 3 suborders and 5 families, in the rice nurseries / main fields in all the locations surveyed. They included herbivores, entomophages and neutrals, and were identified upto the lowest taxa possible.
2. BIODIVERSITY INDICES
The three richness indices, viz., Hill’s number (N0), Margalef index (R1), Menhinick index (R2), four diversity indices viz., Simpson’s index (λ), Shannon’s index (H’), Hill’s diversity No. 1 (N1), Hill’s diversity No. 2 (N2) and five evenness indices (E1 to E5) were used for quantification of arthropod biodiversity in different rice ecosystems during different seasons. Rarefaction method was adopted for working out the expected number of