The focus of today’s Notes from the Lab is a popular one; one of my favorite insects to bring to outreach events and a regular at our encounter cart: The giant prickly stick insect, otherwise known as the Australian Walking Stick or Macleay’s spectre. As their common name would suggest, this species of walking stick is native to northern Australia. The adult females are capable of parthenogenesis, meaning they can clone themselves in the absence of a mate; a trait shared by many phasmids (walking sticks). When they produce their eggs, they will fling them from the treetops, where they will land in the damp soil on the forest floor.
E. tiaratum eggs have a special nodule, which can be seen in the photo above; this nodule is called a capitulum, and is chock full of important lipids and fats that ants find irresistible. The ants find the eggs in the soil, and bring them back to their nest, where they eat the capitulum. Then, they discard the egg in the nest’s waste pile; the conditions of which are perfect for hatching stick insect eggs. When the nymphs hatch out, they even resemble ants; a red head and black body. They are fast and eager to leave the nest before the ants discover an intruder in their midst, so they scamper out and find the nearest tree to climb up. They lose their ant-mimic form after their first molt, which happens in a week or so.
Like many insects that employ camouflage to escape predators, E. tiaratum will often change color according the the background it lives on, though not instantaneously, like we think of when we picture a chameleon. They will gradually assume the appropriate camouflage as they molt. The majority of forms range in shades of brown and tan, but some more extreme forms, like the lichen form above, can be raised under the right conditions (obviously… if they’re surrounded by lichen).
If E. tiaratum is provoked, they will curl their tails over their abdomen in an attempt to look like a scorpion; they may also raise their front legs in an assumed “threat pose.” Fun fact: In a scene from Indiana Jones and the Temple of Doom, Willie has to stick her arm through a crevice to pull a lever to save Dr. Jones and Short Round, only to find the crevice infested with… walking sticks? There are lots of other creepy crawlies in this scene, including cockroaches, centipedes, and even a harlequin beetle, but the fact that anyone could be so worked up over a phasmid is beyond me.