Methodology for assessing the suitability of immature stages of Lepidoptera for nocturnal surveying using ultraviolet flashlights

Lepidoptera are highly sensitive to changes in their surroundings, making them excellent indicators of ecosystem health and reflecting driving factors such as climate and land‐use change. However, surveying adult butterflies of certain species presents challenges, including their short flight periods, preference for inaccessible positions, including tree canopies, and dependence on favourable and consistent weather conditions. Other life history stages are generally even more difficult to study.

Researchers have therefore sought to develop different techniques for monitoring species, with nocturnal surveying of larvae and pupae using ultraviolet light (UV) gaining popularity as a simple, inexpensive, and non‐invasive method.

To support the increasing adoption of this surveying technique, we have developed guidelines for conducting nocturnal surveys with UV flashlights focusing on: (1) A scale for assessing the suitability of species for nocturnal UV monitoring which has been validated with photoluminescence emission spectroscopy, (2) Detailed scoring against this scale for over 100 species enabling researchers to use the methodology in the field, and (3) Equipment, including selection of UV flashlight type and 4) Specific recommendations for data collection and reporting.

It is expected that the adoption of this methodology will provide a consistent approach for collecting and reporting data from different sources, thereby facilitating the comparison of results worldwide.