Improving Beneficial Insect Behavior by Reducing Cannibalism in Green Lacewing Larvae using Operant Conditioning at Multiple Life Stages in Various Social Settings

Every year, 40% of all crops are lost due to plant pests and diseases, with pest insects costing the global economy approximately USD 70B. Pesticides have undesirable environmental effects and are becoming less effective against target pests. The use of green lacewings (from the family Chrysopidae) as biological pest control has risen recently, but the cannibalism displayed in lacewing larvae contributes to their low survivability rates and variability in performance. This can be addressed through behavioral conditioning. Citronella oil disrupts hunting behavior by interfering with lacewings' olfactory receptors and can be utilized to condition lacewings without harming them. Y-Maze bioassays indicated that when all four experimental groups (first instar solitary, first instar grouped, second instar solitary, and second instar grouped) were combined, behavioral conditioning was successful at reducing their cannibalistic tendencies towards lacewing eggs by 82% (p < 0.001). On average, the lacewings trained in solitary environments reduced their cannibalistic behavior by 87% (p < 0.01), while those trained in environments with other lacewings reduced their cannibalistic behavior by 77%, with the p-value indicating near-significance (p = 0.0513). The lacewings conditioned at the second instar effectively reduced their cannibalistic behavior by 99% (p < 0.01), but those conditioned at the first instar did not, with an average reduction of 65% and a p-value indicating near-significance (p = 0.0542). These results indicate that lacewing larvae are capable of learning through citronella-based behavioral conditioning and their cannibalistic behavior can be more effectively reduced when they are trained at the second instar in solitary settings. This study’s implications align with efforts to utilize green lacewings as biological pest control in agricultural settings and their role in the global effort to reduce our pesticide dependency and combat pest-induced crop loss.