Influence of Habitat and Climate on the Spatial Distribution of Outbreaks of the Hylesia metabus Moth, Responsible for Lepidopterism, in Coastal French Guiana

Understanding the environmental context of insect outbreaks is crucial, particularly for pest species with significant impact on human health. The ashen moth Hylesia metabus is a generalist Lepidoptera, of which the females have urticating scales (setae) that cause severe dermatological reactions, and its outbreaks thus pose serious public health challenges along the coastal regions of Venezuela and French Guiana. Despite the species' broad distribution throughout northern South America, outbreaks remain unpredictable and localized. Here, we explored factors that correlate with the spatial distribution of outbreaks by investigating 13 sites in French Guiana. We assessed forest structure, tree species composition, canopy cover, and avian predation rates in the field. Additionally, we performed species distribution modeling to explore the effect of climate. Outbreak-prone sites were associated with overall low tree densities, limited daily temperature variation, pronounced seasonal changes between the dry and rain seasons, and, surprisingly, higher avian predation rates which may be more indicative of favorable landscape structure. These conditions are more prevalent along the coast of French Guiana, contrasting sharply with the stable and diverse inland rainforest ecosystems where outbreaks are rarely reported. These findings highlight habitat features consistently associated with outbreaks and provide a first step toward identifying ecological conditions that may influence outbreak propensity and can inform future monitoring strategies under changing environmental conditions.