Behavioral insights into the capture mechanisms of semiochemical-baited flight intercept traps: a case study using Monochamus spp. (Coleoptera: Cerambycidae)

Effective monitoring and surveillance of insect populations is critical for mitigating the threats they pose to ecosystems and economies. Flight intercept traps, including Lindgren funnel traps and cross-vane panel traps, are widely used in surveillance and monitoring programs for forest beetles. Their performance varies among species and the mechanisms underlying their function remain poorly understood. Previous research on trap design effects has predominantly relied on end-point assays, which fail to capture the behavioral processes driving trap performance and often result in oversimplified or teleological explanations, thereby limiting improvements in trap design. We developed and applied a simple 3-step model of trap function to understand the effects of trap design: (i) approach, where insects initiate directed movement toward the trap; (ii) capture, where contact with the trap results in either capture or escape; and (iii) retention, where captured insects remain in the trap or escape. Using observational experiments in the field, we investigated the behavioral responses of Monochamus spp. (Coleoptera: Cerambycidae) to intercept trap designs and collection cup treatments. Observation of beetle approaches to intercept traps revealed that a higher proportion of beetles progressed from 1 m to trap contact with panel traps compared to funnel traps, while escape rates from both wet and dry collection cup treatments were negligible. These findings highlight the importance of behavioral observations in improving our understanding of trap function and identifying features that enhance performance. By providing a mechanistic framework for insect-trap interactions, this work supports the development of more effective tools for monitoring insects.