Australian plague locust

The Australian plague locust (Chortoicetes terminifera) is a native Australian insect in the family Acrididae, and a significant agricultural pest. Adult Australian plague locusts range in size from 20 to 45 mm in length, and the colour varies from brown to green. In profile, the head is higher than the thorax, and the thorax has an X-shaped mark. The legs have a reddish shank and the wings are clear other than for a dark spot on the end. The locusts occur naturally in far northwestern New South Wales and the adjoining areas of Queensland and South Australia, as well as Western Australia. From these areas, the locusts can expand from time to time to be found in the agricultural areas of South Australia, New South Wales, including the Riverina, and Victoria. The locust can be found in a variety of grassland and open wooded habitats across the inland areas of the Australian mainland. Upper-level winds may occasionally carry locusts to coastal areas of the mainland and northern Tasmania and may establish populations in the eastern valleys of the Great Dividing Range; these populations usually fail to establish themselves for more than a few generations. Adult locusts feeding on green shoots that follow rain within 24 to 48 hours in warmer months will mature and lay eggs within 5 to 7 days of a rain event. Using their ovipositors to drill a hole, locusts lay their eggs in the soil in a pod. Pods contain around 30 to 50 eggs and locusts lay two or three pods, 5 to 10 days apart. Egglaying often happens en masse, with as many as a million laid in a hectare of suitable soil. In good conditions (i.e. warm and moist), eggs take around two weeks to develop. After hatching, the nymphs take around 20–25 days to complete development in mid-summer. The locust has five instars, with the wings becoming more prominent with each moult. After the first and second instars, nymphs form aggregations known as bands; these tend to disperse by the fifth instar. Late-instar bands travel up to 500 m per day. Drier country has large bands congregating that are visible from the air, while in the agricultural regions, bands tend to be smaller. After its final moult—6 to 8 weeks after egglaying—the adult locust is called a fledgling. Fledglings have three development stages; a growth phase, where wings are strengthened and the exoskeleton hardened, a fat accumulation stage, and lastly, oocyte development. Gregarious populations of locusts form swarms, recurring in central Eastern Australia once every two or three years. The Australian plague locust is less gregarious than other locust species and swarms occur in a continuum from dense swarms through a range of densities down to scattered adults. Swarms may persist for days, dispersing and reforming while following the wind. Swarms may move up to 20 km in a day. Swarms can infest areas up to 50 km2 (19 sq mi), although typical infestations are less than 5 km2 (1.9 sq mi). Swarms can travel up to 800 km (500 mi), tending to move with hot winds and generally towards the coast in most cases.