Journal of Insect Conservation

ARE PAN TRAPS COLORS COMPLEMENTARY TO SAMPLE COMMUNITY OF POTENTIAL POLLINATOR INSECTS?

Short title: PAN TRAP COLORS AND POLLINATORS

Eduardo Freitas Moreira1*, Rafaela Lorena da Silva Santos1, Uiré Lopes Penna1, Catalina Angel-Coca1, Favízia Freitas de Oliveira1, Blandina Felipe Viana1

1 Zoology Department, Federal University of Bahia, UFBA, Salvador, Bahia, Brazil

*

Detailed description of the reflectance and UVA fluorescence of the white, blue and yellow pan traps.

This appendix aims to explore some spectral properties of the colored pan traps used to capture insects. The spectral reflectance of the pan-traps was characterized through a high-resolution Spectroradiometer Field Spec 4 Hi-Res with 3 nm spectral resolution and range 230-2500 nm. The reflectance measures were taken from fifteen pan traps of three colors i. e. white, yellow and blue, five traps of each color. The traps were described by the reflectance curves, the average proportion of reflectance (xρ) on the peaks of each curve and average proportion of reflectance (xρ) to each range of colors from the near ultraviolet (UVA) to visible spectrum. Additionally, the fluorescence of the color paints and the plastic material used in the pan traps construction was evaluated with a UVA lamp of 46 W in an otherwise completely dark room with a Canon EOS 50D DSLR camera and a Canon EF28-135 f/3.5 lens using 56 mm focal distance. The raw data is available on the support information Table S2 and Figures S3, S4, S5, S6.

The white, yellow and blue pan traps show reflectance peaks at the wavelengths 426 (ρ = 86 %), 528 (ρ = 98 %) and 456 (ρ = 48 %), respectively (Figure S1). The white traps exhibit high reflectance in all visible spectra (xρ = 74 %) with the exception of the violet region (xρ = 43 %). The yellow pan traps absorb nearly all photons with weavelengths on the blue band (xρ = 10 %), and exhibit high reflectance on the bands of green, yellow (xρ = 70 %) and red (xρ = 60 %). The blue pan traps are less reflective with the lowest average reflectance, even on the band of blue wavelength (xρ = 43 %), and has high absorption on the bands of violet and wavelengths above to 513 nm (xρ < 20 %).

Figure S1 – Reflectance curve for the pan traps of three colors; Black line - white pan traps; Blue line – blue plan traps; Yellow line – Yellow pan traps; the colored bar below the y axes illustrates the human colors correspondent to the wave lengths.

The paints used in the traps manufacture are UV-fluorescent (Figure S2). This means that they absorb photons with low wavelength such as UVA photons and re-emit them as visible light with higher wavelength between 400 and 500 nm (Valeur & Berberan-Santos 2011). In figure S2B, all light captured by the camera was emitted from the pan traps paint by fluorescence. Note that in this picture, the white pan trap is missing, because it has practically no fluorescence. In the figure S2C, with more exposure given by a wider diaphragm aperture on the camera, there is a fraction of reflection of violet light and it is possible to notice the white pan trap. The captured violet light was emitted by the UVA lamp because this type of lamps does not produce a 100% pure UVA light. In figure S2D there is evidence that the yellow pan traps are the more fluorescent, followed by the blue and white pan traps respectively. This behavior may help to explain why the yellow pan traps exhibit a reflectance peak on the green band (Figure S1). Because of limitations in the spectroradiometer used to take the measurements, we could not encompass the entire Near-ultraviolet spectrum (320 – 400 nm). However, the three trap colors analyzed presented ascending reflectance curves between 400 and 350 nm, indicating the existence of a reflectance peak on UVA band (Figure S1). The absence of fluorescence in the white pan traps also may be associated with its high UVA reflectance.

Figure S2 – Picture of pan traps under white light (A), and UVA light (B – D), showing the differences in fluorescence between the white, blue and yellow pan traps from left to right respectively; A – ISO = 200, shutter speed = 1/5", aperture - f/20; B - ISO = 800, shutter speed = 1", aperture - f/20; C - ISO = 800, shutter speed = 1", aperture - f/10; D - ISO = 800, shutter speed = 1", aperture - f/5.

Considering the pan traps characteristics described above, one can conclude that together, the three colors, cover the visible color spectrum of most insects, especially the Hymenoptera, Aculeata. In general, the Aculeata have a trichromatic visual system with photoreceptors sensitive to the wavelengths on the bands corresponding to UVA (S-receptor, λmax= 330 – 350 nm), blue (M-receptor, λmax = 430 – 450 nm) and green (L-receptor, λmax = 520 – 540 nm) (Chittka & Menzel 1992, Peitsch et al. 1992, Chittka et al. 1994). Therefore, the white pan traps can stimulate the three photoreceptors. The blue pan traps can stimulate the photoreceptors sensitive to UVA and Blue light as the yellow can stimulate UVA and green photoreceptors. In addition, few insects have photoreceptors sensitive to red light (λmax= 592 – 600 nm) (Peitsch et al. 1992). Hence, light reflected from white and yellow pan traps can trigger these photoreceptors.

References

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Chittka, L., a Shmida, N. Troje, and R. Menzel, 1994. Ultraviolet as a component of flower reflections, and the colour perception of Hymenoptera. Vision Res. 34: 1489–508. Available at: http://www.ncbi.nlm.nih.gov/pubmed/8023461.

Peitsch, D., A. Fietz, H. Hertel, J. Souza, D. F. Ventura, and R. Menzel, 1992. The spectral input systems of hymenopteran insects and their receptor-based colour vision. J. Comp. Physiol. A 170: 23 – 40

Valeur, B., and M. N. Berberan-Santos, 2011. A brief history of fluorescence and phosphorescence before the emergence of quantum theory. J. Chem. Educ. 88: 731–738