This week we return to the Amazon basin for another nighttime adventure in the rainforest. The rainforest is a dangerous place for an insect. Hungry monkeys, motmots, and coatimundis search the vegetation for tasty insects. Insects have clever ways of escaping or dissuading other animals hoping to have them for dinner. Monarch butterflies and their larvae contain chemicals toxic to predators. Velvet ants pack a powerful sting. The bright colors both insects sport warn predators not to fool around with them.
Many residents of the rainforest have evolved another way of reducing the risk of being eaten. As we saw in a recent episode, caterpillars of skipper butterflies make leaf rolls to hide from the inquisitive eyes of predators. Others insects have perfected the art of crypsis, and simply blend with background features of their environment. Deep in the forest my trusty halogen torch revealed several cryptic katydids doing remarkable imitations of dead or injured plant leaves. Evolution transmogrified their bodies from an “I’m a bug, come and eat me” look to an “I’m a rotten leaf, look elsewhere for dinner” mien. On one green nocturnal katydid, fore and hind wings came with leaf-like veins complete with discolored patches, apparently the handiwork of some plant-eating insect. Its abdomen bore a serpentine patch that looks like the gallery of a leaf-mining caterpillar. A long curving ovipositor at the rear end and kneeling posture help complete a leafy look that could easily be overlooked by a hungry vertebrate predator.
A bit further down the trail, a brown katydid complete with tattered wings (apparently eaten by a caterpillar) and bespeckled with leaf spots (apparently caused by a fungus) does a magnificent job of imitating a dead leaf. Nearby a detached dead leaf swings on a strand of spider silk making the cryptic deception even more compelling. Next week we will meet other masters of disguise that have selected another common feature of the rainforest to abet their escape from hungry jaws.
With notches and spots on its dusky brown wings, this leaf mimic katydid has a fair chance of being overlooked by a visually hunting predator.
Bug of the Week thanks the crew of the Posada Amazonas for providing the inspiration for this episode. The wonderful book “Insect Defenses” by David Evans and Justin Schmidt was used as a resource for this episode.