Use of a pronotal shield as an extraretinal short-wavelength filter for the dorsal compound eye of an insect

Adaptations of nocturnal insects’ visual systems to dim light environments include increased photon capture and sensitivity. Yet this risks saturation, which is countered by screening pigments limiting the photons reaching the photoreceptors. Male glow-worms must detect the females’ green bioluminescent glow at night to mate. In addition to screening pigments, males possess a differentially pigmented pronotal shield (PS) beneath which they can retract their compound eyes. The possible role of the PS in behavioural regulation of the light reaching their eyes has not, to our knowledge, been investigated. Here, we characterise the spectral filter properties of the PS and combine this with behavioural assays of males’ response to light exposure. We show that the PS acts as a differential filter transmitting longer-wavelengths of light to the compound eyes beneath while blocking shorter-wavelengths. Male glow-worms in the dark or in the presence of green light extend their head but rapidly r..., , # Use of a pronotal shield as an extraretinal short-wavelength filter for the dorsal compound eye of an insect

Dataset DOI: [10.5061/dryad.70rxwdcbf](10.5061/dryad.70rxwdcbf)

## Description of the data and file structure

In this study we combine measurements of light transmission through the darkly pigmented and translucent regions of male glow-worms’ pronotal shield with behavioural assays of the effects of UV/white light exposure to test the potential role of the pronotal shield in reducing the intensity of light reaching the compound eye, and it's behavioural implementation. We demonstrate that the pronotal shield of glow-worms acts as an extraretinal short wavelength filter for the dorsal compound eye.

### Files and variables

#### File: Trackball_raw_data.zip

**Description:** Contains all videos that were manually analysed to obtain males' head position (retracted or extended from beneath the headshield) under different light conditions. Trials all include an initial control ...,