It's odd because it makes an insect that otherwise is very camouflaged much more noticeable. This makes me wonder if it's biomimicry of another dangerous/poisonous/distasteful local insect.
kurt (orionmystery)
More than likely, it's a sexual display/indicator without any "practical" purpose related to survival. Like a peacock's tail. If you're really interested in evolutionary biology, read Darwin's original work. You'll be surprised to learn that most adaptations have little to do with survival.
But this national geographic magazine seems to doubt that theory:
(http://news.nationalgeographic.com/news/2008/02/080222-butte...)
http://en.wikipedia.org/wiki/Peppered_moth_evolution
But then again, the "original experiments behind the peppered moth story" were known to have "widely acknowledged flaws." http://www.truthinscience.org.uk/tis2/index.php/component/co...