Population Growth Parameters, Predatory Potential, and Functional Response of <i>Melanostoma orientale</i> (Diptera: Syrphidae) Against <i>Macrosiphum euphorbiae</i> (Hemiptera: Aphididae) Infesting Tomato

Natural enemies play a vital role in regulating pest populations in agroecosystems. The present study evaluated the developmental biology, population growth parameters, predatory potential, and functional response of Melanostoma orientale (Diptera: Syrphidae) against the potato aphid, Macrosiphum euphorbiae (Hemiptera: Aphididae), under laboratory conditions. The predator successfully completed its life cycle on M. euphorbiae , with an average fecundity of 38.57 eggs per female. The population growth parameters indicated a positive population buildup with intrinsic rate of increase (r) of 0.081 day −1 , finite rate of increase (λ) of 1.084 day −1 , net reproductive rate ( R 0 ) of 13.51 offspring per individual and mean generation time (T) of 31.64 days. The third instar contributed highest to the prey consumption (215.87 aphids), followed by the second (31.94 aphids) and first instar (11.05 aphids). The net predation rate ( C 0 ), transformation rate ( Q p ), stable host‐kill rate (ψ), and finite host‐kill rate (ω) were recorded as 200.06, 16.31, 7.90, and 8.56, respectively. Functional response analysis revealed that all larval instars exhibited a Type II functional response, with a significant negative linear coefficient, indicating a decelerating prey consumption rate at higher prey densities. The attack rate (a) increased from 0.092 to 0.340 h −1 , while handling time (Th) decreased from 4.743 to 0.663 h across successive larval instars, reflecting improved predation efficiency with development. These findings provide valuable insights for further evaluation of this species as a biocontrol agent prior to its application in integrated pest management programmes.