Phasmatodea

Order

PHASMATODEA
(Greek, phasma = apparition, phantom)

Description

All phasmids consume plant material (phytophagous) and are remarkable for their ability to mimic twigs, stems, leaves and sticks. Their bodies are as varied as the vegetation they inhabit. Dry grass stems are inhabited by species that are brown with cylindrical bodies and long tubular legs. Foliage species may have bodies that are flattened and leaf-like with legs that bear equal resemblance to foliage. Wings may be present or absent. If wings are present, then the forewings are leathery and form protective covers (tegmina), the rear pair are used for flight. In winged species, only the males are capable of flight. Compound eyes are present and simple eyes (ocelli) are only present in winged species. Mandibles are well developed. The antennae are composed of short, straight segments (filiform).

Life Cycle

The juveniles emerge from the eggs as miniature, wingless versions of the adults (nymphs) and mature by successive moults. Nymphal stages can be differentiated from adults by their smaller size, fewer antennal segments and in winged species, a lack of wings. Mimicry also extends to the eggs. Many species lay eggs that resemble plant seeds.

Distribution

Stick insects are usually found in warmer parts of the world, especially the tropics.

Food

Phasmids actively feed during the night hours and generally remain motionless during the day. Stick insects feed on fresh vegetation, usually the foliage of the plant on which the insect is found.

Importance

Apart from their use by other organisms as food, phasmids are generally not of any great significance in ecosystems. When present in enormous numbers (which does occur in eucalypt forests at times) damage may be significant. When plague proportions of stick insects are reached, whole tracts of forest can be defoliated and seriously damaged.