Phasmatodea: stick and leaf insects

Characteristics
As their name suggests these cryptic insects have the shape and colouring of the leaves and twigs of the plants they inhabit. Phasmids are distinctive insects and are often large to very large ranging in size from 30 to 300 millimetres in body length. Stick and leaf insects, when discovered will often drop to the ground and remain motionless rather than take flight. Some species will also shed legs when attacked, growing them back over time. Phasmids are distinguishable by the following features:

• Body shape variable but most are elongate and cylindrical or flattened and resemble sticks, leaves or grass

• 2 pairs of wings although some species are wingless

• Wings when present consist of short, hardened forewings which form a protective cover over part of the larger membranous hind wings

• Antennae are filiform and may be either short or long

Phasmid nymphs usually resemble adults but lack wings.

PHASMATINAE are a prominent subfamily of phasmids with an Australia-wide distribution. Most species are large, fully winged and stick-like in appearance. Ctenomorphodes tessulatus is a medium sized stick insect which has a spiny mesonotum and a mosaic patterned hind wing. The males of this species are fully winged and the females either short-winged or flightless.

Life Cycle
Male phasmids are generally smaller than the females and have more functional wings. It is usually the males that will fly around to locate a mate. Female phasmids usually lay their eggs in leaf litter and can lay between 100 and 1000 depending on the species. The eggs may hatch in the same season they were laid or remain in the litter to hatch up to 3 seasons later depending on the conditions. Nymphs moult several times before reaching maturity and development may take from a few weeks up to a few months.

Feeding
All phasmids are herbivores as both adults and nymphs feeding on the leaves of trees and shrubs, although a few species are known to eat grasses. Nymphs favour the younger softer leaves at the tips of branches while adults are able to feed on both young and old leaves. Some populations of stick insect species can grow to such large numbers that they become pests, defoliating entire stands of trees with their voracious appetites.

This species of phasmid has long cerci and fully winged females and can grow up to 25 centimetres in length. Podacanthus wilkinsoni known commonly as the ringbarker phasmid can be distinguished from other stick insects by the orange-yellow patch on the hind wing. This species is known to be a pest of eucalyptus forests as it occasionally occurs in large numbers causing severe defoliation of eucalyptus trees. In heavily infested areas this species has even been known to eat the bark of trees.

Habitat
Stick insects are found over much of Australia where adequate trees and shrubs occur to feed on. Those species known strictly as leaf insects are only found in northern Queensland.

Eurycnema goliath is a conspicuous, heavily built species known as the Goliath stick insect and can be found over much of northern Australia and down the east coast as far as Victoria. Females of this species are fully winged and known to grow up to 25 centimetres in length.