Biology, morphometrics and predation potential of <i>Coccinella septempunctata</i> Linn. (Coleoptera: Coccinellidae) on corn leaf aphid, <i>Rhopalosiphum maidis</i> (Fitch) infesting wheat

The study explored the biological parameters of the aphid-feeding ladybird beetle, Coccinella septempunctata L., focusing on its development, body measurements, cannibalistic behaviour, and predation efficiency against corn leaf aphid (Rhopalosiphum maidis F.) at two temperatures: 25±1°C and 18±1°C. The duration of life stages, including egg, larval, pre-pupal, pupal, and pre-imaginal phases, was shorter at 25±1°C, with egg period 3.30±0.10 days and the entire pre-imaginal stage lasting 17.84±0.23 days. These stages required slightly more time to complete at 18±1°C. The sex ratio at both temperatures favoured females, recorded as 1.2:1 (F:M) at 25±1°C and 1.5:1 (F:M) at 18±1°C. Females underwent pre-oviposition, oviposition, and post-oviposition periods, while males experienced a sexual maturity phase, with temperature affecting their lifespan and reproductive performance. On average, females laid 372 eggs at 25±1°C and 339 eggs at 18±1°C. The study found that cannibalistic behaviour increased with larval age and food scarcity. Both larvae and adults exhibited significant predatory activity against R. maidis. The feeding capacity per larval stage rose progressively from the first to the fourth instar, with fourth instar larvae consuming an average of 168.04±31.27 aphids per stage. Among adults, females consumed 112.20±14.80 aphids per day, while males consumed 84.20±9.04 aphids.