Australian plague locust: identification field guide

Page last updated: Tuesday, 12 June 2018 - 2:13pm

This article describes the main distinguishing features between Australian plague locusts (Chortoicetes terminifera) and other common grasshoppers/locusts.

Lifecycle

The Australian plague locust has three stages in its lifecycle – egg, hopper and adult.

In the south-west of Western Australia the locust can complete two generations each year; the first generation occurring through winter, spring and summer and the second generation through summer and autumn.

Diagram of the lifecycle of the Australian plague locust.
Diagram of the lifecycle of the Australian plague locust

Differences between Australian plague locusts and wingless grasshoppers

Australian plague locusts are sometimes found with a range of other, similar looking species of non-winged grasshoppers. The Australian wingless grasshopper (Phaulacridium vittatum), is often confused with the Australian plague locust, especially at the immature stage.

Australian wingless grasshoppers strongly vary in colour from dark grey to almost black (never green), but 40% of the population have wings and can fly.

At the hopper stage, locusts as well as wingless grasshoppers, are only 15-20mm long and distinguishing features such as shape, colour and wing veins are very variable and hard to see.

Australian plague locusts always have an x-shaped marking behind the head. In nymphs this can be faded and becomes more visible with maturity, but it is always present.

Wingless grasshoppers sometimes have no patterns at all.

A comparison of the Australian plague locust (hopper stage) and the Australian wingless grasshopper.
The Australian plague locust hopper (left) showing the typically saddle-shaped body profile, compared to the Australian wingless grasshopper (right) body profile, which is more straight
Comparison of markings of the Australian plague locust and the Australian wingless grasshopper.
The best field identification of locusts at the hopper stage of development is the X-shaped marking on the back of their thorax. The Australian plague locust hopper (left) has a white X-shaped marking as its main identifier, while marking is more parallel in the Australian wingless grasshopper (right).

Distinguishing Australian plague locusts from other grasshopper and locust species

Adults

Adult Australian plague locusts have a dark spot on the otherwise clear hind wing. The dark spot looks like an elongated smudge. They also have red tibia. This distinguishes them from all other species.

Male Australian plague locusts are 27mm and females are 32mm in length.

Adult Australian plague locust showing dark spot on wing and red tibia
Adult australian plague locust showing dark spot on wing and red tibia

Some Australian locust/grasshopper species from the genus Austroicetes can have similar X-shaped marks but never have a red tibia and a dark spot on the hind wing.

Three commonly Austroicetes species found in the same areas as Australian plague locusts are:

Confusing Austroicetes (Austroicetes pusilla), which have a yellow or pink hind tibia, males are 14mm and females 20mm in length. Rarely found in high densities.

Small plague locust (Austrocietes cruciata), whose colour and pattern are highly variable, hind tibia is usually yellow, males are 14mm and females 25mm in length. This species can be found in high densities, can form swarms but these are not known to move great distances, about 35km is the maximum dispersal rate.

South-eastern Austrocietes (Austrocietes vulgaris), whose colour and pattern is highly variable. Hind tibia has a basal black or brown band, tibia can be reddish in colour. Males are 12mm and females are 23mm in length. This species has been recorded as causing crop damage in concert with other grasshopper/locust species.

Hoppers

Australian plague locust hoppers (third instar) can be distinguished from other hoppers by:

  • transverse bands on the femur
  • posterior (bottom) half of X-shaped marking is distinct
  • lateral (side) surface of head and thorax is mottled
  • hind tibia with light coloured collar

Later instars have more pronounce X-shaped markings on thorax, hind tibia retains collar.

Lateral and dorsal view of Australian plague locust
Lateral and dorsal view of Australian plague locust. Image copyright NSW Department of Primary Industries.

Confusing Austroicetes (Austroicetes pusilla) have:

  • indistinct X-shaped marking
  • hind femur with single black band
  • lateral (side) surface of head and thorax with white triangular marking
  • hind tibia with collar and cross-bar

In later instars background colour remains pale, white triangular markings become indistinct.

Confusing Austrocietes, lateral and dorsal view of first instar
Confusing Austrocietes, lateral and dorsal view of first instar. Image copyright NSW Department of Primary Industries.

Small plague locust (Austrocietes cruciata) have:

  • X-shaped marking on thorax
  • hind femur obliquely banded
  • lateral (side) surface of head and thorax with white triangular marking
  • hind tibia uniformly dark

Later instars have uniformly light coloured tibia.

Small plague grasshopper, lateral and dorsal view of first instar
Small plague grasshopper, lateral and dorsal view of first instar. Image copyright NSW Department of Primary Industries.

South-eastern Austrocietes (Austrocietes vulgaris) have:

  • anterior (top) half of X-shaped marking distinct
  • hind femur transversely banded
  • lateral (side) surface of head and thorax with white triangular marking
  • hind tibia with white collar and cross-bar

Later instars retain general form, hind tibia has white collar and cross-bar.

Southeastern Austroicetes, lateral and dorsal view of first instar
South-eastern Austroicetes, lateral and dorsal view of first instar. Image copyright NSW Department of Primary Industries.

References

Baker, G. L. 1984. Field guide to nymphs of grasshoppers and locusts in New South Wales. Advisory Bulletin 2, Department of Agriculture New South Wales.

Key, K.H.L. 1992. Taxonomy of the genus Phaulacridium and a related new genus (Orthoptera: Acrididae). Invertebrate Taxonomy, vol. 6, 197-243.

Rentz, D.C.F., Lewis, R.C., Su, Y.N., & Upton, M.S. (2003) A Guide to Australian Grasshoppers and Locusts. Natural History Publications (Borneo). Kota Kinabalu.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080