Firefly species (Lampyridae) vary in the color of their adult bioluminescence. It has been hypothesized that color is selected to enhance detection by conspecifics. One mechanism to improve visibility of the signal is to increase contrast against ambient light. High contrast implies that fireflies active early in the evening will emit yellower luminescence to contrast against ambient light reflected from green vegetation, especially in habitats with high vegetation cover. Another mechanism to improve visibility is to use reflection off the background to enhance the light signal. Reflectance predicts that sedentary females will produce greener light to maximize reflection off the green vegetation on which they signal. To test these predictions, we recorded over 7500 light emission spectra and determined peak emission wavelength for 675 males, representing 24 species, at 57 field sites across the Eastern United States. We found support for both hypotheses: males active early in more vegetated habitats produced yellower flashes in comparison to later-active males with greener flashes. Further, in 2 of the 8 species with female data, female light emissions were significantly greener as compared to males.
Field site locations
Four-letter location codes (Code), colloquial names (Location), exact GPS coordinates (Latitude and Longitude) and the total number of male individuals (#), regardless of species, measured in each of the 57 populations. In addition, the number of individuals of P. pyralis, P. scintillans and P. marginellus collected at each field site are shown in the last three columns respectively. Total = 675 male individuals. Please note that some field sites are on private land and the corresponding author should be contacted for details concerning access to those sites. Footnotes: * only lab-reared larvae from Unknown Photuris parents captured at this locality were measured. $ habitat was not categorized at this locality. % GPS coordinates available upon request from Charles H. Wharton Conservation Center.
Dryad_Hall_et_al_2016_Locality.csv
Individuals per species
The total number of individuals measured for each species: males (M), females (F), and larvae (L). In three individuals, remnant larval light organ emissions were measured in adult males (LM) or females (LF). Total = 786 individuals representing 25 species, including 675 males in 24 species.
Dryad_Hall_et_al_2016_Individuals_Per_Species.csv
Spectra data
List of specimens for which spectra were measured. Sex/larva column indicates whether specimen was a larval individual (L) or an adult male (M) or female (F). LM and LF indicate that a larval light organ was measured in an adult male or female respectively. Activity time (Act) is for the population from which the specimen was caught and is coded as 0 for start of activity beginning prior to 30 minutes after sunset and 1 for activity beginning more than 30 minutes after sunset. Habitat (Hab) is for the population from which the specimen was caught and is coded as 0 for open, 1 for mixed, and 2 for closed habitats. Also shown are the number of spectra measured per individual (#), and the mean (Peak lambda) and variance (Var_lambda) of the peak emission wavelength for each specimen. Identification number (ID #) corresponds to KSH collection; NC indicates individual not collected. Location code from Table S1. SF = Single Flash.
Dryad_Hall_et_al_2016_Spectra_Data.csv