[ukmicky (OP)]

Moths outshine  butterfly's in the beauty stakes but you would think it would be the other way round since moths are active during the night when there colours cant be seen.

Why are moths so colourful.
 

[dentstudent]

My intuitive (but not necessarily correct) answer covers 3 points:

1: sex - to attract a mate (but how at night?)
2: camouflage - to avoid being eaten during the day
3: avoidance - to advertise their distastefulness or to scare away predators

Are all moths nocturns? I'm not sure that they are. Hummingbird moths are active during the day for example.

Also, (just for the sake of arguement) I'm not sure I agree that all moths are that pretty. Some are, well, a bit dull.

[dentstudent]

Another thought might be that the strong colours are ones that best show up to a moth of the opposite sex in moonlight (ah, romance!) and are therefore more approporiate for mating? It's just coincidence that they look pretty to us during the day.
Flowers are attractive to bees in wavelengths outside of our optical range, but are still pretty to us. Maybe this is the case for moths also.....

[Karen W.]

That could be! it is entirely possible.