This is a very large family of nocturnal moths that come in a wide variety of sizes with wingspans ranging from 12 to 120 millimetres. All geometrids have a uniform shape and stance, which is characteristic of the family. The forewings of these moths are broad and triangular in shape with hind wings almost as broad. During the day all geometrids hold their wings outstretched and flat against the surface they are resting on, with the top of the forewing forming an almost straight line at right angles to the body. Many adults are green in colour, often with mottled patterns which when combined with their posture allows them to blend with their surroundings, making them very cryptic.

Geometrid caterpillars are known as loopers due to their method of locomotion. Unlike other caterpillars, geometrid larvae have a gap between their thoracic legs and their prolegs at the end of the abdomen and as a result move by a series of loops. The front of the body is stretched out and held in place with the 3 pairs of true legs and then the back of the body is brought forward so the prolegs at the rear can grasp the surface near the front legs. These caterpillars are often also called 'inchworms' because of this motion and the scientific name of this family means 'earth measurers'.

Phallaria ophiusaria (brown leaf moth)

Geometrid caterpillars are plant feeders and can often be seen during the day mimicking twigs by remaining erect supported by their prolegs among the foliage of their food plant. This species can be found during the day resting motionless on wattles (Acacia species), hopbush (Dodonaea species) and Hakea species, looking much like a dead twig.

For more looper species visit the Australian Insect Common Names - Geometridae section found here.