Caterpillars Can “Blink” A Fake Eye

22373_origMany animals have a fake eye — or eyespot — or two that they can use for protection from predators, often by frightening or distracting the hungry creature. Eyespots are especially common among tropical caterpillars. And researchers conducting a caterpillar inventory in Costa Rica have documented two species (Eumorpha phorbas, above, and E. labruscae) in which the eyespots can sort of blink. They report their findings in the Journal of Natural History.

How can an eye that’s not real blink? To find out, Thomas J. Hossie of Carleton University in Ottawa, Canada, and colleagues collected and reared caterpillars of the two species. When each species reaches the last instar before turning into a moth, it takes a form that has an eyespot on a tentacle that pops up from its butt; this is known as the anal horn. For the study, the researchers would remove a caterpillar from its rearing bag, let it acclimate for a minute, and then prod its rear three times. The result was a “blink,” such as the E. labruscae captured in the video below:

“Both caterpillars can ‘blink’ their posterior eyespot upon perceiving a threat,” Hossie writes on his blog Caterpillar Eyespots. “That is, they can move the skin around the eyespot such it either conceals/reveals the eyespot or flashes (i.e. reflects light) conspicuously towards an onlooker.”

Being able to blink the eye would make it look more like a mammal or bird eye, which is a little odd because scientists had thought that the eyespots on caterpillars were supposed to look more like snake eyes. Snakes can’t blink because they don’t have eyelids. Unfortunately Hossie and the other researchers haven’t been able to test how predators respond to these distinctive eyespots — including whether they might interpret them as mammal, bird, or snake — because these are really rare species.

But Hossie notes on his blog that these caterpillars have another defensive trick that is truly snakelike: “Interestingly,” he writes, “both Eumorpha caterpillars also inflate their thoracic body segments, while pulling their head into their body, to form a diamond shape which appears similar to the head shape of dangerous co-occurring snakes (at least to human observers).”

Image copyright CAPEA, used with permission under Creative Commons license

This Moth Has Better Hearing Than A Bat (Or Anything Else)


The greater wax moth (Galleria mellonella) is locked into a high-frequency, evolutionary battle with the bats that prey upon them. Bats emit ultrasonic for the purpose of echolocation, sending out sounds at frequencies as high as 212 kHz. Now scientists have discovered that not only can the great wax moth hear the bats’ echolocation calls, but the moths can hear even higher frequency sounds, up to 300 kHz. The research team from the University of Strathclyde in Glasgow, Scotland report their findings in Biology Letters.

Such auditory sensitivity is “unprecedented,” the scientists write. No known bat produces sounds at that high a frequency, so why the moth evolved to hear such sounds is a bit of a mystery. But the researchers suspect that the super-hearing helps the moths avoid predators or communicate with each other, perhaps in courtship.

“The use of ultrasound in air is extremely difficult as such high frequency signals are quickly weakened in air,” the lead researcher James Windmill said in a statement. “It’s not entirely clear how the moths have developed to be able to hear at such a high frequency, but it is possible that they have had to improve the communication between each other to avoid capture from their natural predator – the bat – which use similar sounds.”

Image courtesy of Sarefo via Wikimedia Commons