Species richness, diversity and evenness of predators in Bt cotton in Maharashtra, India

Ten types of predators which feed on different insect pests of cotton were recorded. The most abundant predators were coccinellids (32.92%) and spiders (30.66%) followed by predatory bugs (10.29%), syrphids (8.87%), chrysopids (7.19%), preying mantid (3.89%), robber fly (2.01%), dragonfly and damselfly (1.55%), wasp (1.51%) and long-legged fly (1.13%). Margalef Richness Index was highest during November (1.42). Menhinick Index ranged from 0.38 to 0.47. Simpson's Index was highest in July (0.64) and lowest in September, October and November (0.23). As index was high in July, the diversity was low in July. The diversity of predators was maximum in September, October and November. The highest Shannon-Weinner Index was noticed in October month (1.74). The evenness indices (Pielou's Index and Simpson's Evenness) was highest in October month.