Saturday, October 11, 2014

A murderous, mobile lichen

I've written about the larvae of the Green Lacewing, Leucochrysa pavida, before, but never with (what I felt) were adequate photographs. These little creatures are very hard to image. They're small, mostly covered up, and when they expose themselves they're generally on the move.

It was time to figure out how to overcome the photographic challenges. I'm involved in a project that features an essay about lacewing larvae, and a good photo was a must. Lacewing larvae of the type shown below are not rare, but can be a challenge to locate for reasons that will soon be obvious. I asked Chris Bedel, Director of the Edge of Appalachia Preserve, if he might keep an eye out for lacewing larvae and capture me some livestock if he found any. Chris did, and I was able to set up a shoot under more controlled conditions than one would find outside, on the trunk of a tree. My rig was the Canon 5D Mark III with the twin-lite flash setup rigged to the spectacular MP-E 65 mega-macro lens. Still wasn't easy, and I probably shot off a hundred shots to get a few keepers.

Not much to see here. At least that's what the lacewing wants you - or its victims - to think. Just a little roundish knot of lichens on a lichen-encrusted tree bark substrate.

Whoa! The little lichen ball lives! In one of the more remarkable cases of camouflage in the insect world, this predatory larva adorns its body with lichen bits. Not just any lichens, either. One study showed that only three species are typically selected. The lacewing is quite adept at harvesting these lichen bits, and swinging them up onto its dorsal surface, where they are webbed into place with silk.

The end result is a lichen Ghillie Suit. The insect moves with a halting stumble-step that might remind a birder of the curious mincing paces of an American Woodcock. Looking up under the costume, as here, we see that the lichens conceal a formidable predator. Check those mandibles!

Lacewing larvae of many species prey on aphids, and this one is no exception. Its only problem is that ants often guard arboreal aphid colonies, as the ants get a reward of nutrient-rich aphid honeydew for their troubles. Ants are extremely good at warding off threats to their charges; entomological pit bulls, you might say. The lacewing larva gets around this problem by means of its camouflaged suit. It moves right into aphid colonies, fooling the ant guards with its outstanding disguise. Other potential victims are no doubt fooled as well. Who would notice that the little lichen clump was slowly moving their way?

We go directly under the animal, and can better see how everything is put together. Not only is the lacewing incredibly well camouflaged, but it can also flex its body and pull the lichen suit into a protective shell if threatened. Under my macro lens, I could see the larvae occasionally harvest a lichen bit with the mandibles or labial palps - little feelers that extend forward from the head (it was hard to tell what parts were doing the grabbing) - and quickly place them on its back.

The death-dealing mandibles at the right are what the creature uses to seize its prey, which will then be punctured by the mouthparts and sucked dry. Radiating around its body are long struts capped with stiff hairlike bristles. These serve to support the lichen "house" on its back.

Should you be a lesser beast, you would not want to glance up and see this face looming from under the "harmless" clump of lichen.

If all goes well for the lacewing larva, it will eventually morph into a small but beautiful winged insect with gossamer net-veined wings that is extremely different than the animal seen here. If you search enough lichen-spackled tree trunks and limbs, eventually you'll make the acquaintance of one of these things.

Nature truly is amazing.

Thanks to Chris Bedel for his help in securing these lichen-lions!

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4 comments:

Jacqueline Donnelly said...

Wow! What incredible photos! I hope someday to see one in the flesh. I always search very closely among clusters of Wooly Alder Aphids, where Lacewing larvae are known to disguise themselves by covering themselves with the waxy white "fur" that these aphids exude, so as to hide undetected from guardian ants and feast freely among the flock, like a wolf in sheep's clothing.

Anonymous said...

I live in Surfside Beach, South Carolina and have seen these ever-so-slowly crawling on my deck. I have two out there right now and decided to take a minute to look up these little amazing creatures. Thanks for the info! Mystery solved!

Anonymous said...

I just saw one of these and it was shocking to me! Thanks for your posting, your pictures are awesome!

espo said...

Hello sir, I just photographed and got video of the little guy walking on my deck. I live in upstate South Carolina and have never seen the little guy before. Thanks for helping me solve the mystery of what the spec was walking on my deck.