Predation Response of Macrolophus caliginosus Wagner (Hemiptera: Heteroptera: Miridae) Across Multiple Prey Density Levels of Aphis craccivora Under Fixed Temperature Conditions

Abstract Macrolophus caliginosus Wagner (Hemiptera: Heteroptera: Miridae), a predatory bug widely used in biological control against whiteflies and spider mites, also shows strong efficiency on aphids, with females consuming on average ~43.2 first-instar Aphis gossypii nymphs per day under laboratory conditions. This study evaluates the predation capacity and functional response of M. caliginosus to varying densities of Aphis craccivora , aiming to assess its potential as a biological control agent against this significant agricultural pest. The research examines how each instar’s predation rate responds to three temperatures (20 °C, 25 °C, and 30 °C) and five prey density levels (5, 10, 15, 20, and 25). Predation rates were measured by exposing individual predators to different prey densities and recording the number of aphids consumed daily. Functional response parameters, including handling time ( T h ), search rate ( α ), and the average number of prey killed ( H a ), were calculated using Holling’s disc equation. This study is a laboratory-based investigation conducted under controlled conditions. Macrolophus caliginosus nymphs showed a clear Type II functional response against Aphis craccivora , with first instars exhibiting the highest predation efficiency, consuming significantly more aphids than older instars, At 20 °C, predation capacity increased with prey density, peaking in the first instar and declining in later instars; at 25 °C, consumption patterns fluctuated, with reduced efficiency in higher instars; and at 30 °C, predation rates varied, with some instars showing improved efficiency. Functional response parameters revealed that the first instar had the shortest handling time at 20 °C, indicating high efficiency, while efficiency decreased at 25 °C and improved at 30 °C. The second instar showed enhanced predation at 25 °C but slightly reduced efficiency at 30 °C. The third instar exhibited high efficiency at 20 °C, declined at 25 °C, and partially recovered at 30 °C. The fourth instar consistently had the lowest predation rates and longest handling times across temperatures, improving efficiency at 30 °C; These findings underscore the interplay of temperature, prey density, and predator instars in determining predation rates. The data highlights the adaptability of M. caliginosus to environmental changes, providing critical insights for applications in biological pest control under varying climatic conditions.