Stick insects or phasmids eat leaves and resemble leaves or sticks.
They make a great addition to any classroom or home and are easy to maintain. This information is provided to help you incubate, raise and maintain these amazing invertebrates all while learning about their biology.
'Stick Insects in your classroom’ is a Video Conference program available to primary schools in NSW.
The biology of Stick Insects
There are estimated to be approximately 200 species of phasmids in Australia with a total worldwide number of 3000 with new species being discovered by scientists regularly.
Phasmids are found in a range of habitats and have adapted to both resemble and feed on a variety of plant species. Some, such as the Goliath Stick Insect are found in the forested areas of eastern Australia, there are also species which occur in arid, coastal and monsoonal environments. Most phasmids feed on either or both Eucalyptus (gum trees) and Acacia (wattles) however some are specialists such as the Peppermint Stick Insect, Megacrania batesi, which only eats the leaves of the Screw pine, Pandanus tectorius, and receives its name from the peppermint-like smelling secretion it produces when alarmed.
Australian stick Insects range in size from a few centimetres long to the longest species; the Titan Stick Insect, Acrophylla titan, which can grow up to 250mm from head to tail, and often appear longer when the front legs are stretched forward.
Phasmids are related to other groups of insects including mantids, grasshoppers, crickets, katydids and cockroaches. These insect groups share a common trait in having young that are similar in shape to the adult form and do not have a life-cycle that includes a larval stage like most other insect groups such as bees, wasps, flies, ants, moths, butterflies and beetles.
Phasmids are often confused with mantids because they are both experts at blending in. The two groups are remarkably different in ecology and how they feed themselves. Phasmids are herbivores, whereas mantids eat other animals. The differences become clearer once you start to look a little closer; the eyes of mantids are large and prominent, and are situated at the ends of a triangular-shaped head, providing mantids with excellent vision and the ability to judge distance. The front legs of mantids are folded forward, giving the impression that they are praying, which is why these insects are often called ‘praying mantis.’ These front legs have sharp barbs and can spring forward quickly . These are great adaptations for detecting and grabbing fast moving prey, which usually includes insects, even phasmids.
One of the reasons why mantids are confused with phasmids is because both groups of insects are superb examples of using camouflage for survival. While mantids use their skill of blending in to avoid predators as well as remaining undetected by their potential prey, phasmids only use camouflage as a defence against being seen by predators and therefore becoming a meal. Phasmids have the general features of the leaves and sticks of the plant that they hang from and feed on.
Once a phasmid believes that it has been seen there are a few tactics that they employ to avoid being eaten. Males can fly away when stressed, but females cannot escape predators so easily and so will attempt to try to blend in to the background of twigs and leaves by swaying in a regular motion which may help the animal blend in with its surroundings. Although female phasmids cannot fly few are wingless and will use a sudden flickering of the wings to startle potential predators, many species also achieve this by having a concealed colourful stripe under the wings which is only visible during defensive displays.
Some species have spikes on the hind limbs, which can be used to physically deter a predator from eating them through inflicting sharp painful ‘kicks’. This occurs only in the longer and heavier species and can be found in both Australian and overseas species.
All phasmids begin life as an egg which is dropped from the end of the females abdomen and falls to the ground at the base of the tree or shrub. Thousands of eggs are laid during the females life. The eggs of the Spiny Leaf Insect, Extatosoma tiaratum, have a knob, called a capitulum, which is attractive to ants. Ants carry the eggs back to their underground nests, eat only the knob, and leave the rest of the egg in the nest, protected from other animals that might eat it. The young phasmids (also known as nymphs) hatch after one to three years underground and look and behave like red-headed black ants. They emerge from the ant nest and climb rapidly upwards, looking for soft green leaves.
Many female phasmids do not need to mate in order to produce fertile eggs. This form of reproduction is called parthenogenesis and all the eggs produced will hatch into females. If the females do mate with a male before producing eggs, the nymphs (babies) may be male or female.
Once the young phasmid have reached the leaves of a food tree, they moult into a green or brown, slow-moving leaf mimic. Moulting involves a new skin forming under the old skin, which will split along the back, while hanging from a branch the young stick insect needs to carefully pull it’s body and legs out of the old skin. Once free of the old skin, the new skin will be soft and over a period of time will expand and harden Most females live for about 18 months, while the males are only short-lived, surviving for around 6-8 months.
Raising your stick insects
Care of eggs
Eggs should be kept in a shallow container with a secure lid to stop hatchlings wandering. Small holes in the lid will provide air to the eggs, however holes are not needed if the container is opened every second day. The eggs can be placed on newspaper or sand and the container should be located in a position where the teacher and students can check to see if any have hatched at least on a daily basis.
Phasmid eggs will hatch at room temperature, however not all eggs will survive, this is why the females lay so many eggs, which increases the chances of producing surviving young. To improve the chance of producing healthy hatchlings the eggs should be lightly sprayed with water once a week. However if there is any sign of mould the eggs should carefully be removed, the container should be washed with soapy water, rinsed well, dried and the sand or newspaper should be replaced before returning the eggs to the container.
Care of young
Once the young insects (nymphs) have emerged from their eggs they should be transferred to their enclosure. Nymphs can be picked up using a clean, dry paintbrush and should not be handled until they are mature. Leaves should be provided as soon as they hatch as they will begin feeding immediately, however care should be made to ensure that tiny insects do not wander into and drown in the container holding the leaves. This problem can easily be solved by using a clump of plastic cling-wrap which can be wedged around the food branches around the container.
Phasmid nymphs can be kept in small plastic enclosures with their food plant, however they need enough space for moulting to hang on the food plant about three body lengths from the bottom of the enclosure. As the insect grows this distance becomes larger so in the long run it is best to begin with an enclosure that can house the total number of adults you intend to keep.
Housing your stick insects
Before the eggs have hatched you need to prepare a house for your stick insects. There are a variety of ways to house and display stick insects, the two main factors to consider are; that stick insects need airflow and require enough space for both the insects to hang comfortably as well as enough space to hold at least one container of food plants. In order to keep up to twelve stick insects an enclosure 90cm high with a 60cm² base is required.
A number of pet stores now sell mesh and glass terrariums which make great homes for stick insects. These terrariums have the advantage of being able to add locks and lighting, however can be expensive and are only useful if they are of suitable size.
Stick insect enclosures can be constructed from glass, wood as well as flyscreen and aluminium framing. These can be built to your desired size will be functional as long as the following guidelines ate followed:
- At least one side should be mostly made of fibreglass or aluminium flyscreen to allow airflow.
- Young insects are small so there should be no gaps larger than 0.5mm, no gaps are better as droppings could accumulate in gaps of this size.
- Surfaces should be waterproof enough to tolerate regular spraying and to allow cleaning.
- The door needs to open easily and seal snugly. It should be large enough to remove the food branches and the water container.
One of the easiest ways to provide suitable housing for phasmids is to use a small aquarium placed on its side. A door constructed of plywood, plastic or metal can be made to fit the open side. A large part of the door (70-90%) should be cut out to make a window of flyscreen for ventilation. Hinges and a latch can be siliconed to the aquarium to make sure that it fits tightly with no gaps.
Feeding your stick insect
Eucalyptus (Gum) leaves are eaten by all phasmid species that are commonly kept in the classroom and the home. Although gum trees seem to be abundant in most towns and suburbs, it is surprising how few branches are at a reachable height and so you should check to make sure that you will be easily able to feed your insects without needing special tools or ladders. It is also a good idea to have several trees that you collect branches from, this way you do not denude a small number of trees of their foliage which can harm the trees and make your neighborhood look unsightly. Make sure it is legal to collect the leaves you are using.
Branches of leaves should be harvested from healthy looking trees that are located in habitat that is free of any chemical spraying or other pollution. Fresh healthy-looking leaves will last longer and have more nutrition than old dry leaves. If the leaves are not to be used straight away they can be kept sitting in a bucket of water in a fridge for up to a week before use.
Be sure to investigate what kind of trees you are using and how to spot healthy leaves. Note that young small leaves can contain higher levels of eucalyptus oil which are harder for phasmids to digest. Give the branch a good shake before feeding them to your stick insects as there are often animals living on the branches. Tiny jumping spiders are beautiful little hunters that can prey on young phasmids.
Presenting the leaves
The branches should be cut to the right size and placed in a container such as a vase or jar filled with water to keep the tips of the branches wet. The leaves should last about a week, longer if the leaves are freshly cut from the tree and if the water in the container is regularly changed.
Removing the old branches and changing the leaves is the most time-consuming part of keeping stick insects. It is easy to throw the phasmids out with the old branches and at first the task of taking each insect off individually and placing it back in the enclosure will seem daunting, however it is possible to train the eyes to spot the particular shape of young phasmids on the branch, remember their instinct will be remain motionless and they are particularly good at not being seen.
One way to make the task easier is to take the branches out in the morning and sit them in a bucket, once you have placed all the larger and more obvious insects back into the enclosure you can leave the bucket for a few hours. Over time the smaller phasmids will move toward the top of the branches and can be placed in the enclosure as they are found. Another strategy is to have two containers, in one the new branches are placed and over a few days the stick insects will move from the older leaves to the new leaves, making branch removal easier.
Watering your stick insects
Phasmids drink droplets from the leaves and can be watered by providing them with a daily misting using a spray bottle. Too much moisture can lead to mould which can harm phasmids.
Maintaining your stick insects
Every few weeks the bottom of the enclosure needs to be cleaned out. The insect droppings (also known as frass) and eggs can be scooped up and placed in a container. The eggs will need to be removed before you throw out the frass, sand or newspaper. You can then set up the eggs as described above. The glass and other surfaces should be cleaned as well, which can be done with paper towel and water. If detergent is used it should be rinsed thoroughly with water. The enclosure should be dried out before returning the leaves and phasmids.
Handling your stick insects
Phasmids are easy to handle safely without harming their delicate bodies, the trick is not to handle them but to let the insect walk onto you and grip your hand. Phasmids can be taken from a branch, leaf or surface of the enclosure by placing a flat palm in front of the insect, unless the insect is stressed and unwilling to be handled the front legs should grip your hand and the insect will walk onto your hand. Phasmids are most comfortable hanging upside down and so will stay still. Remember; let the stick insect do the handling.
Phasmid species often kept in the classroom and the home
Spiny Leaf Insect
Also known as ‘Macleay’s Spectre’ after Naturalist and Australian Museum Trustee (1841-62) William Sharp Macleay and its ghostly appearance. This harmless insect was used to terrify movie-goers in the 1984 movie Indiana Jones and the Temple of Doom and is one of the most interesting and sought-after phasmids kept around the world. Females are wingless and are very different in shape to the slender male.
The eggs have a knob, called a capitulum, which is attractive to ants. Ants carry the eggs back to their underground nests, eat only the knob, and leave the rest of the egg in the nest, protected from other animals that might eat it. The young phasmids (also known as nymphs) hatch after one to three years underground and look and behave like Red-headed Black Ants. Spiny Leaf Insects eat eucalyptus leaves but have also been raised on rose and raspberry leaves by keepers overseas where eucalyptus is not always available.
Children's Stick Insect
Like the Spiny Leaf Insect, this species has a high degree of ‘sexual dimorphism’ which is the difference in size and shape between males and females. In this species the females look like 'leaves' and males look like 'sticks'. Children’s Stick Insects are easy to keep and both males and females are easy to handle, just don’t be surprised if the males like to fly off your hand. The eggs are elongated, tan capsule-like and young are bright green to whitish-green. This species feeds and blend in well on eucalypt leaves.
Goliath Stick Insect
One of the largest species of stick insect in Australia with females growing over 200mm. These insects make spectacular display animals due to their impressive size and vivid green and gold markings. Males have similar colour and patterning but are smaller, have wings and are capable of flight. The eggs of this species are large (3mm), have a grainy bark-like texture and are cylindrical in shape. The young are brown and stick like and remain so until they under go their final mature moulting phase.
Goliath Stick insects will feed on Eucalyptus and females are hardy and tolerant of handling however some individuals can become cranky when agitated and will rapidly open their wings to reveal a pinkish-red stripe. In some cases when a female is threatened she may compress the handlers fingers and palm with the sharp spikes on the hand which can be painful, however this is not usually encountered in Goliath females that are handled properly with care.
Margin-winged Stick Insect
These are the true 'sticks' of the stick insect world and will blend in to become invisible on any branch. The females grow to around 175mm and have long bodies that are uniform brown without any markings or features. The males are shorter, more slender and have slender folded wings which they will readily use to take flight.
A rapid flash of the small wings of the female will be used as a defensive display once she is aware that her camouflage is not working. Margin-winged Stick Insect eggs are around 2mm long, smooth and black in appearance. The young are green for the first few weeks of life. This species does not have any special care requirements and will eat eucalyptus leaves.
- Brock, D. 2000. A Complete Guide to Breeding Stick and Leaf Insects. Kingdom Books. Havant.
- Brock, D. and Hasenpusch, J. 2009. The Complete Guide to Stick and Leaf Insects of Australia. CSIRO Publishing
- Henderson, A. Henderson, D. and Sinclair J. 2008. Bugs Alive, A guide to keeping Australian invertebrates. Museum Victoria. Melbourne.
- Matthews, R. W., Flage, L. R. and Matthews, J. R. 1997. Insects as Teaching Tools in Primary and Secondary Education. Annual Review of Entomology, 42, 269-289.