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Walking Leaves

10th February 2016

Walking leaves is something we associate with a science fiction movie. In this case, our photography turns science fiction to science fact! During an Untamed Photography field session deep in the heart of the Peruvian Amazon rainforest, many miles NW of Puerto Maldonado up the Las Piedras River in forest managed by the Las Piedras Biodiversity Station, we encountered many small creatures of extraordinary shapes and sizes simply asking to be photographed! Take for example a leaf-mimicking Katydid; a stunning creation of nature. This particular insect is a great subject to photograph during one of our field tutorial sessions because it remains so still for so long (unlike say most frogs, which jump away in seconds or minutes). Keeping still actually enables it to better conceal itself, with its colouration making it blend so well with its surroundings – the trick is highly impressive when you see it! Our guest photographers learn how to frame, shoot and capture great shots of jungle creatures such as this in natural light and with flash. Here we have examples from such tutorial sessions with several specimens of this type of insect.

With our DSLR Canon 70 & 7D’s, with ISO set to 200, shutter speed at 100, f-top at 11, and a trusty tripod, we capture some great shots of these insects side-on, really expressing their textures and fine colouration, which are so leaf-like it’s uncanny. They are able to mimic live or dead leaves, and even the mould that grows on some of the latter – an adaptation to an environment full of arthropod predators. Throughout the teaching sessions, hundreds of images were taken and our guests learnt some of the tricks of the trade of macro-photography in humid tropical rainforests.

Facts: Here in the Peruvian Amazon, these miracles of nature are part of a group of insects known as the Pterochrozini, which mimic leaves. Amazingly these insects not only mimic new green leaves, they have perfected the evolutionary art of mimicking decaying and chewed up leaves too. Most have elytra with a vein pattern similar to many leaves, and some even have elytra with holes in them or chunks missing, to mimic decaying or eaten leaves. As you might expect, no two individuals are alike. In fact individuals of one species can vary so greatly in appearance that in the past nearly 25% of newly named species were latter found to belong to a pre-existing one. Now why would a species exhibit so much diversity? In this case predation breeds innovation. The principle predators of the leaf-mimicking Katydids are monkeys, such as Squirrel monkeys (Saimiri sp.). Primates are very smart and systematically comb through vegetation looking for tasty insects like katydids. If all katydids imitated a leaf in the same way, the monkeys would quickly learn how to identify a fake leaf. But when every individual’s fake is different, the task becomes much more complex. Interesting, huh?

Story written by Mark Fernley