Being a jungle out there, flying insects are at nocturnal risk from a colossal number of ‘echo-locating’ bats. For survival-sakes, many species have adapted auditory sensitivities that extend into ultrasonic frequencies. For some insects, these auditory receptors have developed into sound-producing assets. More than merely listening devices, they can also respond with ultrasonic clicks to either confuse or deter bats. Some have even further evolved for communication during courtship.
The Privet Hawk Moth (Psilogramma menephron) is such a sound-producing moth. Like so many Daintree Rainforest inhabitants, its successfulness is delivered by the qualities of its design. Cryptic coloration provides excellent camouflage on the trunk of a tree during the day, to be safe from the ever-vigilant gaze of a multitude of birds. At night it produces sounds to confuse bat’s audio-perception, but it can also communicate with potential mates.
Of course, successful passage through the caterpillar phase is prerequisite to metamorphosis. Reaching between 90 to 110 mm, its final (green) instar larval form has disruptive camouflage of white diagonal stripes that break the greens into separate shades to become convincingly leaf-like. Preliminary to the process of pupation, the green coloration gives way to browns and the whites to yellows. Over the next couple of days, transition to the pupal phase will complete to a dark brown translucent pupa with a narrower proboscis sheath, which both harden and darken for security amongst the leaf-litter on the forest floor. Emergence of the adult moth can take between two and four weeks.