The walking sticks and leaves!

I think stick bugs fascinate just about anyone who encounters the little “copycats”. I have found that the more you know about something, the more you appreciate it. In that vein I would like to look into detail about some little known stick bug facts

Description

Stick and leaf insects have long stick-like bodies that grow between three centimetres cm and 30 cm in length. Their bodies resemble leaves, sticks or grass, which makes them extremely good at camouflage.  Usually they are brown or green in colour and they have two pairs of wings, although some species are wingless.

Life Cycle

Female stick insects are generally larger than the males. The males can usually fly really well and will zoom around looking for females. Female stick insects lay hundreds of eggs, which are dropped from their abdomen down onto the ground where they lay among the leaf litter waiting to hatch. Some species will glue their eggs to sticks and leaves or bury them in the soil.  The young stick insects are called nymphs and look just like the adults only much smaller and with no wings.  Nymphs have to shed their skin (just like a snake) every few weeks so that they can grow larger.

Who needs males?

One of the most interesting things about stick insects is their ability to reproduce parthenogenetically. This is a form of asexual reproduction where the unfertilised females produce eggs that hatch into females. If a male fertilises the egg, it has a fifty-fifty chance of turning out male. If no males are around, the line continues with females only!

Favourite foods

Stick insects are herbivores, which mean they only eat plants. They are the vegetarians of the insect world and love to feed on leaves, grasses and sometimes even flowers and bark. Many stick insects are nocturnal which means they do most of their feeding at nighttime to avoid predators like birds.

Defence tactics

Stick insects make a tasty snack for many animals such as birds, lizards, frogs, spiders and ants. Because they have so many enemies, stick and leaf insects have developed some pretty cool ways to defend themselves.

Stick insects, as their name implies, are insects that have taken camouflage and imitation to the extreme by developing the appearance of a stick or twig. Typically these insects are shades of brown, although some may be green, black, gray, or blue. You might think that stick insects hide among sticks on the ground, hoping to blend in, but most stick insect species are found sitting right out in the open within the leaves of a tropical tree. They usually stay perfectly still, but when they need to move, they are even able to camouflage their motion. It is common to see them walk in a swaying motion, pretending to be a twig caught by the wind. Other stick insect species have lichen-like outgrowths on their bodies that help camouflage them on tree bark.

Other forms of protection

When camouflage is not enough, some stick insects use active forms of defence to handle predators. Some species can release an awful-smelling brown liquid. Other species have brightly coloured wings that are invisible when folded against their body. However, when they feel threatened, they will flash open their wings then immediately drop to the ground and again hide their wings. The predator is often confused as it searches for a brightly coloured insect but only sees a pile of drab, brown sticks on the ground!

The concealable egg

You’ve probably realised by now that stick insects have developed adaptations to fool predators. Clever ways to lay eggs are also included in their bag of tricks. Female stick insects use two main methods of laying eggs: dropping eggs on the ground or placing them in a hard-to-reach place. Some stick insect species will drop one egg per day somewhere on the ground during their day’s travels. These eggs are commonly small and resemble seeds. By dispersing her eggs far and wide, the female prevents a predator from lunching on a cluster of her eggs.

Other females lay their eggs in places that are hard for predators to find. For example, some stick insects will lay eggs in the soil, in hollow parts of plants, or glue them to bark or the underside of leaves. Species that lay their eggs underneath leaves tend to hatch faster than species that lay eggs elsewhere, as the eggs need to hatch before the leaf falls off the tree and exposes the eggs!

Most stick insect eggs are covered by a hardened shell with a node called a “capitulum” on one end. The capsule of some species contains fats and other goodies that lure ants.

The ants will bring the capsule underground into their nest, remove the capitulum, and feed on the nutrients it contains. After they are done eating, the ants toss what’s left, which includes the stick insect egg, in their nest garbage dump area. The egg incubates in the safety of the ant nest, out of sight of predators. A few months later the all-but-forgotten hatchling makes its way out of the ant nest!

Stick insects hold the record for longest insects in the world.

In 2008, a newly discovered stick insect species, Phobaeticus chani or Chan’s megastick from Borneo broke the record for longest insect. One specimen held in the Natural History Museum in London measures an incredible 567 millimetres. This measurement is however with the front legs fully extended. The body still measures an impressive 357 millimetres.

Kudzai Mafuwe is Curator/Entomologist at the Natural History Museum of Zimbabwe