Striped eel catfish (Plotosus lineatus). Photo © Hectonichus
Both the striped eel catfish and the zebra longwing butterfly rest gregariously in dim light and are so poisonous that they are avoided by predators.
Although neither species could be described as a colonial organism, the warning colouration – consisting of striping – of both species is likely to work only as a collective pattern.
This is because their bodies are too small and their stripes too narrow to make them particularly conspicuous as individuals even in bright light.
Robin and the Honey Badger, 22 March 2016

Striped eel catfish (Plotosus lineatus). Photo © Hectonichus · Wikimedia Commons · CC BY-SA 3.0

Zebra longwing (Heliconius charithonia). Photo © Diego Delso · Wikimedia Commons · CC BY-SA 3.0
