Monday, July 18, 2011

Two very cool beetles

The world is full of cool beetles. I mean, REALLY full of these hard-shelled little - and sometimes big - charmers. The order Coleoptera is huge; it contains some 400,000 described species and experts think that that many again, if not more, have yet to be described. In many habitats, beetles are the most numerous type of animal. A great many are tiny and nondescript, apt to be passed by without ever being seen.

Not these two.

A trio of pleasing fungus beetles, Megalodacne heros, are undoubtedly quite pleased to be enjoying a fine repast of budding shelf fungi. Last year, I had the great fortune of having one of the other species of pleasing fungus beetle visit the sphere of my front porch's light - SEE HERE - but this species far outdoes Megalodacne fasciata in sheer grandiosity. These three were part of a small herd that I encountered back in June in the Great Smoky Mountains National Park.

Up close and personal with the business end of a pleasing fungus beetle at the chow line. This animal displays classic aposematic - warning - coloration. The carapace is boldly ornamented in brilliant orange, forming a striking and very obvious contrast with the gloss black base coloration. The jarringly conspicuous coloration pattern, coupled with its diurnal - daytime - habits and fearlessness, strongly suggest that this is a beetle that you do not wish to eat. As many species of fungus are toxic, I assume that these beetles are too.

The pleasing fungus beetles were certainly cool, but they may be trumped by these golden tortoise beetles, Charidotella sexpunctata. They aren't big - it'd take a few dozen to make one of the aforementioned pleasing fungus beetles - but they sure are neat. In this photo, a pair works diligently to ensure that more tortoise beetles grace our landscapes. This species noshes on plants in the morning-glory family, and if you've got morning-glories in your garden, you may have your life enriched by these wee beetles.

In 1979, entomologist Edward Barrows published a wonderful paper on this species, and another similar tortoise beetle. You see, tortoise beetles are chameleonlike and can change color, which adds greatly to their allure. Barrows documented that a tortoise beetle can shift its colors in as little as 12 seconds. When all is well and they're having fun, such as in this photo, a bronzy-gold metallic cast is normal. As light plays over the beetle, glancing off its shell at different angles, a rainbow of blues, greens, and even purplish tints are reflected back.

In the course of making these photos, I felt it necessary to horn in and reposition the beetles for better photo ops. They didn't like it, and when I disturbed the pair, this male went from the rainbow display of the former photo to this dull blood-red coloration in seconds. Apparently these color shifts are accomplished by forcing fluids into tiny cells, or chambers, in the carapace which in turn changes the way that light refracts off the shell. How cool is that?

Beetles may be small, but they certainly can be sublime.


Kathy McDonald said...

Nice photos and post..I see a great presentation about Insects and Beetles in your future, maybe at some conference?:)

Derek Hennen said...

Interesting, the literature I've found on the pleasing fungus beetles has described them as nocturnal, not diurnal. When I found one a few weeks ago it was at night, feeding on some fungus. They're very pretty beetles, the colors are striking.

Jim McCormac said...

Who knows, Kathy? I wouldn't want to bug anyone with such a talk :-)

I wonder if that varies by species, Derek. The one that came yp my porch light last year was Megalodacne fasciata, a smaller species, and it was clearly active at night. The much bigger species that's the subject of this post was obviously active in the middle of the day. A friend just sent along photos of this same species, feeding during day s well.

Derek Hennen said...

It might differ by species, though the one I collected at night was M. heros as well. I saw it about a half hour before sunset, though it was definitely dark in the forest.