Diversity in conformity: Meet the Hologram Moth

Green-backed Looper by day, Hologram Moth by night

Learning a new group of insects is always a challenge, but some groups are easier than others. Moths are a special challenge because there are so many of them. As of 2010, Greg Pohl and his coauthors have documented 2367 species of Lepidoptera in Alberta and more are added each year. The vast majority of these are moths, but 175 or so are butterflies.

Flash-induced iridescent 'hologram' style Diachrysia balluca Geyer, 1832

Like all living organisms, moths show individual variation within a species, some genetic, some the result of developmental or ecological experiences. Many moths also seem to exhibit a general convergence in patterns among various species and genera.

A pair of 'Carpet Moths', mystery moth on left, Dysstroma hersiliata (Guenée, 1858) on right

This is particularly striking in the many species of moths with forewing patterns that seem to break up their outlines and allow them to blend into the background where they rest during the day - on tree trunks and limbs, among lichens or dead leaves, on the ground, or in a shadow somewhere. Presumably much of the variation in colour and patterns in the wings results from natural selection that improves the survival of moths with patterns appropriately cryptic for the places they like to rest.

Also known as the Large Brassy Plusia, another Diachrysia balluca under the black light

Bird predation is known to have been a primary factor in the classic example of the Peppered Moth (aka Pepper & Salt Geometer) becoming the Carbon Black Moth in industrial England. As the smoke from coal fires coated the bark and branches of light-coloured trees, the white & black patterned Peppered Moth populations became dominated by melanistic forms - dark as coal dust. More impressively, as clean air laws and the change to other fuels resulted in a drastic reduction in particulate pollution, the Peppered Moth morph again became the more common. Such switching between two morphs is easy to understand, but the seemingly random variation in patterns is less so.

A Green-Arches resting on a grill - probably not its natural resting place

These BugGuide Green Arches Anaplectoides prasina (Denis & Schiffermüller, 1775) are a nice example of variations within a theme. No two moths are exactly the same, yet the underlying patterns are all similar. I'm guessing these moths like to rest on lichen covered surfaces, but it is hard to think like a bird, and perhaps they see it differently. Not much seems to be known about where moths hang out during the day; however, the preponderance of grey to brown to buff patterns resembling bark and lichens among the mid to larger moths seems suggestive.

Aposematic Virgin Tiger Moth Grammia virgo (Linnaeus, 1758)

Not all moths are cryptic, of course, but often the reason for being bold is clear. The Virgin Tiger Moth above, for example, is positively shouting "Do't eat me: I taste badddd!", although that probably wouldn't help much in the dark and one wonders what a bat would think? Spicy?

What is this Hologram Moth trying to tell me?

And I wonder what birds and bats think about the Green-backed Looper? I know what I think - if you are going to use a flash to take pictures of this moth, you will need a flash diffuser. Other than that, though, I find this looper confusing. It is very large for a Plussine, so presumably would make a good meal for a bird or bat. Having now seen the moth resting during the day (picture at the top), however, I'm guessing it may like to hide among dying or damaged leaves. I've got no idea why it has such a strange hairdo though.

Party time at the black light

References
Grant BS. 1999. Fine tuning the Peppered Moth Paradigm. Evolution 53: 980-984. http://bsgran.people.wm.edu/melanism.pdf

Majerus MEN. 1998. Melanism - Evolution in Action. Oxford University Press, NY. http://www.amazon.ca/Melanism-Evolution-Michael-E-Majerus/dp/0198549822

Miller K. The Peppered Moth - An update. http://www.millerandlevine.com/km/evol/Moths/moths.html

Pohl GR, Anweiler GG, Scmidt BC & Kondla NG. 2010. An annotated list of the Lepidoptera of Alberta, Canada. ZooKeys 38: 1–549.
http://www.pensoft.net/journal_home_page.php?journal_id=1&page=article&type=show&article_id=383&abstract=1