Swallowtail Caterpillars

It was recently discovered that the mystery behind the resemblance of a young swallowtail caterpillar larva to bird droppings, and then later in life as an adult, appearing as a replica of the leaves they live on, is not so secret anymore. The disguises are due to a hormone called Juvenile hormone, researched and made public by Japanese scientists, and keeps larvae of the butterfly Papilio Xuthus, commonly found in Japan, in their black and white appearances until maturity. According to many of these researchers, reason for this seemingly instinctive camouflage could be to protect and defend the young caterpillars from predators such as hungry birds until they are able to mature and become mobile. One scientist, Haruhiko Fujiwara of the National Institute of Agro biological Sciences in Japan, who took part in the discovery and exposé of the hormone, stated in an e-mail "We found that juvenile hormone works as a switch for the camouflage pattern. That is a novel aspect of this hormone," as an explanation for the caterpillars’ transformation into its mature green leaf phase, triggered by decreasing levels of the hormone as the swallowtail reaches its last phases of development.

Juvenile hormones were previously known to control different aspects of the swallowtail’s evolvement as it matures, such as molting (when an insect sheds its outer shell) and metamorphosis (when a caterpillar becomes a butterfly) in addition to the newly discovered camouflage process. Fujiwara further wrote that the hormone could even regulate genes involved in color, pattern and surface formation of the butterfly.

In my opinion, it is amazing how a simple insect such as the swallowtail caterpillar can undergo such a miraculous metamorphosis as is their transformation from a larva to a butterfly. It is fascinating how something that passes itself of as an object as repulsive as bird droppings, can slowly develop into something completely different and beautiful. Nature in itself teaches us the moral that beauty is often misinterpreted. The task these scientists face to discover the secrets organisms such as these caterpillars hold and how they can relate to our own human existence must be exciting and intriguing at the very least.