Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is a major pest of several economically important crops with worldwide distribution. Use of insecticides is the principal strategy for its management, which has subsequently led to insecticide resistance and control failures. Functional response of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) at larval and adult stages was evaluated in this study, using S. litura eggs as the prey at various temperatures varying between 15 and 35 °C. Based on logistic model findings, linear parameters of various predatory stages of H. axyridis at various temperatures were significantly negative, which indicate a type II functional response. The theoretical maximum number (T/T_h) of eggs consumed increased with increasing temperature across all predatory stages. According to the random predator equation, the coefficients of attack rate increased and that of handling time decreased as the temperature increased. The 4th instar and adult stages were superior candidates for biocontrol of the target prey, typically at higher temperatures. The maximum attack rate (0.546 ± 0.058 h⁻¹) and lowest handling time (0.189 ± 0.004 h) were exhibited by the females at 30 and 35 °C, respectively, whereas these parameters were inferior for early instars. These findings clearly depict that the 4th instar and adult predators are efficient egg consumers and can serve as potential suppressors of S. litura field populations. The limitations of the predictions formulated by functional response trials are also discussed.

In the current study, we investigated the functional response ofHarmonia axyridisadults and larvae foraging onAcyrthosiphon pisumnymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response.Harmonia axyridislarvae and adults exhibited Type II functional responses toA. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instarH. axyridisconsumed the most aphids. For fourth instar larvae and femaleH. axyridisadults, the successful attack rates were 0.23 ± 0.014 h⁻¹and 0.25 ± 0.015 h⁻¹; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and femaleH. axyridisand the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

Except of pest control, insecticides have shown adverse effects on natural enemies as well. Thus, risk assessment of pesticides for biological control agents is critical for effective use in integrated pest management (IPM) schemes. In the present study, the lethal and sublethal effects of chlorpyrifos, a commonly used insecticide that may negatively affect biological control agents, were evaluated on a non-target predator, the Asian ladybeetle Harmonia axyridis. Previous studies have reported on lethal concentrations, but the effects of sublethal concentrations remain unclear. Lethal and sublethal concentrations of chlorpyrifos were applied to third instar larvae of H. axyridis, and different growth and developmental parameters were measured. Treatment with LC₁₀ (4.62 mg a.i. L⁻¹) significantly shortened the developmental period of third instar larvae, whereas it significantly prolonged those of fourth instar larvae and pupa. Treatment with LC₃₀ (9.59 mg a.i. L⁻¹) significantly increased the larval and pupal developmental period compared with that of the control, whereas feeding potential, female fecundity, and adult longevity significantly decreased after LC₁₀ and LC₃₀ treatment. The pre-oviposition period significantly increased compared with that of the control. Population growth parameters, the finite (λ) and intrinsic rate of increase (r) and the net reproductive rate (R₀), decreased following exposure to sublethal concentrations of chlorpyrifos. According to the results, the use of chlorpyrifos in IPM schemes requires further research because even sublethal concentrations of this insecticide were harmful to H. axyridis population growth.

A two-sex life table is a useful tool for studying the fitness of predators. Previous studies of Orius strigicollis Poppius (Heteroptera: Anthocoridae) fitness have not been done on Pectinophora gossypiella (Lepidoptera: Gelechiidae) using a two-sex life table tool. This study reports the fitness of the minute predatory flower bug, O. strigicollis when feeding on the cotton pest P. gossypiella using a two-sex life table tool. Different densities (5, 10, and 15 eggs) of P. gossypiella eggs were used to calculate the feeding capacity and fitness of O. strigicollis in the laboratory at 28 °C ± 1, 75 ± 5% RH and 16:8 (L:D). The results concluded that O. strigicollis is an efficient predator of P. gossypiella. The maximum growth capacity of the predatory bug O. strigicollis was attained when it was fed on 10 and 15 P. gossypiella eggs. Furthermore, shorter generation and development time were also observed in the case of 15 eggs of P. gossypiella. These results suggest that O. strigicollis has considerable predatory potential and prefers feeding on P. gossypiella eggs than on the first instar larvae at the fourth instar or the female stage. Although the field potential of O. strigicollis is still unknown, this study will support future investigations in terms of field applications.

Functional responses are central to predator–prey dynamics and describe how predation varies with prey abundance. Functional responses often are measured without regard to prey size (i.e., body mass) or the temperature dependence of feeding rates. However, variation in prey size within populations is ubiquitous, and predation rates are often both size and temperature-dependent. Here, we assessed functional responses of larvae and adultHarmonia axyridison the 1st, 2nd, and 3rd instars of the preySpodoptera lituraacross a range of temperatures (i.e., 15, 20, 25, 30, and 35°C). The type and parameters of the functional responses were determined using logistic regression and fitted to the Roger's random predator equation. The magnitude of predation varied with the predator and prey stage, but prey predation increased with warming and predator age. Predation by the female and 4th instar ofH. axyridison the 1st instar of prey was greater, followed by the 2nd and 3rd instar of preyS. litura. No predation occurred on the larger prey for the 1st, 2nd, and 3rd instars ofH. axyridis. The larvae and adultH. axyridisproduced a type II (hyperbolic) functional response curve across all temperatures and the three prey types they consumed. Space clearance rates, handling time, and maximum predation rates ofH. axyridischanged with temperature and prey size, increasing with temperature and decreasing with prey size, suggesting more predation will occur on younger prey. This study indicates an interactive role of temperature and prey/predator size in shaping functional responses, which might complicate the planning of effective biocontrol strategies against this serious pest.