Studies were undertaken on the diversity of coccinellids in agricultural and horticultural crops in Madurai and Theni districts of Tamil Nadu State in Southern India during 2004 and 2005. A total of 19 species of predatory coccinellids were recorded including Coccinella transversalis Fab., Menochilus sexmaculata Fab., and Brumoides suturalis in field and vegetable crops and Anegleis cardoni Weise, Nephus regularis Sicard, Chilocorus nigrita Fab. and Jauravia sp. in fruit crops. Crops like tomato, bhendi, guava, sapota and pomegranate had a rich abundance of coccinellids in Madurai, while chillies, cowpea, blackgram and bittergourd in Algarkovil. Higher species richness was registered in citrus and mango in Periyakulam. The equitable distribution of coccinellid species (species evenness) was high in tomato, chillies, blackgram, bittergourd and mango in Madurai; in rice, bhendi and cowpea in Alagarkovil and in citrus, guava, sapota and pomegranate in Periyakulam. The diversity of coccinellids was higher in tomato, bhendi, chillies, blackgram, bittergourd, mango and pomegranate in Madurai; in rice and cowpea in Alagarkovil and in citrus, guava and sapota in Periyakulam. Rank abundance values revealed that C. transversalis, Micraspis discolor Fab and B. suturalis were dominant taxa in weeded and partially weeded rice eco-system whereas M. sexmaculata, C. transversalis and B. suturalis were the more persistent taxa respectively in cowpea ecosystem. The diversity of coccinellids was found to be greater in partially weeded plots than in weeded plots, particularly during the successional stage of crop growth and recorded less diversity during early vegetative stage. Community turnover of coccinellids increased in both ecosystems but at a faster rate in partially weeded canopy.