Subject: Re: Purpose of Scales?

From: Julian Vincent <[email-masked]>
Date: 5 Jun 1996 11:11:49 GMT

I had always understood that since the lepidoptera manage to sequester so many plant 
secondary metabolites (poisons, etc) they made a big thing of warning colouration in 
its various forms in order to realise the usefulness of this biochemical protection 
agains their major predators - birds.  They then go into all the mimicry area, some 
ending up as clearwings mimicking wasps.  This isn't true for all lepidoptera.  For 
instance the blue butterflies are obviously much more difficult to see against a 
blue sky, combined with the flash effect as they open and close their wings during 
flight.  But once again it's the bird predators which are being addressed.  I can 
imagine that scales (a) allow a more plastic response to changing biochemistry of 
colour either during development or evolution, (b) make them more difficult to 
grasp, as evidenced by brown butterflies found with beak marks on the hind wings 
where they have been attacked by a bird going for the eye spots.
Well, it makes yer think, I spose.

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From: Patrick Foley <[email-masked]>
Date: Thu, 6 Jun 1996 21:40:11 -0700

The present advantages of scales are numerous. They certainly provide a
discrete tiling system so that very precise color patterns may arise. But
the primitive Lepidoptera were moths of probably drabber color and
nocturnal habit. Thermal insulation was very likely the original
advantage. Scales occur on the wings and bodies. This insulation (the
veins of wings contain haemolymph) and the substantial oiliness of moths
may be part of the same adaptation to the cool of night.

patrick foley
[email-masked]