Abstract

Rice agroecosystems harbour diverse arthropod communities that perform essential ecological functions, including both phytophagous pest species and beneficial organisms providing natural pest regulation. This study evaluated arthropod community structure across rice fields subjected to three management regimes: thiamethoxam (neonicotinoid), dimethoate (organophosphate), and untreated control. Arthropods were sampled biweekly from 2 to 12 weeks after transplanting using vacuum sampling, pitfall traps, and sweep nets. Shannon-Wiener diversity indices ranged from 1.03 to 2.87, indicating moderate diversity levels across all treatments. The thiamethoxam treatment consistently exhibited lowest diversity indices, particularly at 12 weeks after transplanting (H' = 1.03), while control plots maintained relatively higher diversity throughout most sampling periods. Family Alydidae dominated herbivore assemblages (11.5-14.2 individuals), Family Coccinellidae constituted the most abundant predator group (11.2-16.4 individuals), and Family Braconidae represented the predominant parasitotic taxon (7.6-11.8 individuals). Insecticide applications significantly reduced beneficial arthropod populations, with neonicotinoid exposure producing more pronounced suppression than organophosphate treatment. These findings underscore the importance of selective insecticide use within integrated pest management frameworks to conserve natural enemy populations while maintaining effective pest control in rice production systems.