The functional response of the predator Chrysoperla externa (Neuroptera: Chrysopidae) is influenced by the developmental stage of its prey, Diatraea saccharalis (Lepidoptera: Crambidae)

The sugarcane borer, Diatraea saccharalis (Lepidoptera: Crambidae), is one of the most important pests of sugarcane in the Americas. Among its natural enemies, green lacewings (Neuroptera: Chrysopidae) are frequently observed in infested fields, where they actively prey on this pest. Despite their potential, the effectiveness of lacewings against different developmental stages of D. saccharalis must be assessed before their incorporation into augmentative biological control programs. In this study, laboratory experiments were conducted to evaluate how the developmental stage of D. saccharalis influences the functional response of first-, second-, and third-instar larvae of Chrysoperla externa (Neuroptera: Chrysopidae). Since Diatraea saccharalis larvae initially feed on leaves and only penetrate the stalk after the second instar, eggs and neonate larvae were used in the experiments. Attack rates, handling times, and the number of prey consumed were recorded over a 24-hour period at eight prey densities (1, 2, 4, 8, 16, 32, 64, and 128 individuals), using either eggs or larvae as prey. First- and second-instars C. externa exhibited a Type III functional response when preying on D. saccharalis eggs, and a Type II response when preying on larvae. In contrast, third-instar larvae showed a Type II response for both prey types. Attack rates were similar between eggs (0.0079/h) and larvae (0.0095/h), while lower handling times (0.2048 h for eggs and 0.2168 h for larvae) and higher estimated numbers of prey attacked (117.2 eggs and 110.7 larvae) were observed for third instars. Overall, our laboratory results indicate that C. externa has potential as a biological control agent for D. saccharalis.