Methodology for assessing the suitability of immature stages of Lepidoptera for nocturnal surveying using ultraviolet flashlights
Data files
Jun 05, 2026 version files 1.70 MB
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260513_All_figures_data_reproduction.zip
1.69 MB
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README.md
2.70 KB
Abstract
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; 3) Equipment, including selection of UV flashlight type; and 4) Specific recommendations for data collection and reporting. It is expected that adoption of this methodology will provide a consistent approach for collecting and reporting data from different sources, thereby facilitating the comparison of results worldwide. This dataset is the spectroscopy undertaken to support the methodology presented in this article.
Dataset DOI: 10.5061/dryad.dbrv15fhp
Description of the data and file structure
Spectroscopy with 365 nm and 385 - 395 nm flashlights
Fluorescence spectroscopy was performed in a free-space setup using UV flashlights for excitation. All larvae specimens tested were in their final instar and were gently clamped and positioned at a fixed distance from the UV source. Specimens were illuminated obliquely over an area of approximately 10 mm², and fluorescence was collected vertically and relayed to the spectrometer via free-space optics. A 450 nm long-pass filter was used to suppress scattered UV excitation. Spectra were acquired using a Czerny–Turner spectrometer (Andor Shamrock 500i, 300 lines/mm grating) paired with a CCD camera (Andor iDus 401). Broadband spectra were obtained by stitching spectra recorded at multiple grating positions, yielding an overall spectral range of 450–900 nm. The intrinsic spectral resolution was approximately 3 nm; however, the effective resolution was ~5 nm after application of a 5 nm Gaussian smoothing filter to reduce high-frequency noise. Background spectra were acquired with the specimen removed and subtracted from the measured spectra to remove ambient light and residual fluorescence from the experimental setup. Spectra were intensity-normalized prior to stitching to account for minor intensity variations. Fluorescence intensities were normalised to variations in UV excitation intensity using a calibrated photodiode. Raw intensity values were retained used for exploratory analysis relevant to potential field detection. Excitation-wavelength-dependent measurements were not feasible due to insufficient signal after spectral filtering.
Files and variables
File: 260513_All_figures_data_reproduction.zip
This directory contains a self-contained figure reproduction script for the spectrometer data shown in the manuscript.
Contents:
reproduce_plots.pyrebuilds the stitched spectra from the raw TXT files and regenerates the figure panels.raw_data/contains the raw spectrometer files required for those figures.figures/is the output directory for regenerated SVG figures.processed_tabulations/is the output directory for tab-separated curve exports.
Run from this directory with:
python reproduce_plots.py
The script is confirmed to work with
- Python: 3.12.3
- scipy: 1.16.3
- numpy: 2.3.4
- pandas: 2.3.3
Running the script regenerates the figure files and the processed tabulations in the directories above.
Fluorescence spectroscopy was performed in a free-space setup using UV flashlights for excitation. All larvae specimens tested were in their final instar and were gently clamped and positioned at a fixed distance from the UV source. Specimens were illuminated obliquely over an area of approximately 10 mm2, and fluorescence was collected vertically and relayed to the spectrometer via free-space optics. A 450 nm long-pass filter was used to suppress scattered UV excitation. Spectra were acquired using a Czerny–Turner spectrometer (Andor Shamrock 500i, 300 lines/mm grating) paired with a CCD camera (Andor iDus 401). Broadband spectra were obtained by stitching spectra recorded at multiple grating positions, yielding an overall spectral range of 450–900 nm. The intrinsic spectral resolution was approximately 3 nm; however, the effective resolution was ~5 nm after application of a 5 nm Gaussian smoothing filter to reduce high-frequency noise. Background spectra were acquired with the specimen removed and subtracted from the measured spectra to remove ambient light and residual fluorescence from the experimental setup. Spectra were intensity-normalized prior to stitching to account for minor intensity variations. Fluorescence intensities were normalised to variations in UV excitation intensity using a calibrated photodiode. Raw intensity values were retained used for exploratory analysis relevant to potential field detection. Excitation-wavelength-dependent measurements were not feasible due to insufficient signal after spectral filtering.