Turns out those rainbow-splashed colors that reflect off of insect wings- the ones I’ve been seeing for years and not thinking much of- may serve a communication function:
These extremely thin wings reflect vivid color patterns caused by thin film interference. The visibility of these patterns is affected by the way the insects display their wings against various backgrounds with different light properties. The specific color sequence displayed lacks pure red and matches the color vision of most insects, strongly suggesting that the biological significance of WIPs lies in visual signaling.
It also just so happens that I had a photo in my archives (above) perfectly illustrating the phenomenon. The reflections are visible against the dark background but not the light background.
source: Shevtsova, E., Hansson, C., Janzen, D., & Kjaerandsen, J. (2011). Stable structural color patterns displayed on transparent insect wings. Proceedings of the National Academy of Sciences, 108 (2), 668-673 DOI: 10.1073/pnas.1017393108