Australian Plague Locust - Life-cycle

Life-cycle

Adult locusts— feeding on green shoots that follow rain within 24 to 48 hours in warmer months—will mature and lay eggs within five to seven days of a rain event. Using their ovipositor to drill a hole, locusts lay their eggs in the soil in a pod. Pods contain around 30 to 50 eggs and locusts lay 2–3 pods, 5 to 10 days apart. Egg laying 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 instar, nymphs will form aggregations known as bands; these tend to disburse by the fifth instar. Late instar bands will travel up to 500 metres per day. Drier country will see large bands congregate that are visible from the air while in the agricultural regions, bands will tend to be smaller.

After its final moult—6 to 8 weeks after egg laying—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 will 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 kilometres in a day. Swarms can infest areas up to 50 square kilometres (19 sq mi), although typical infestations are less than 5 square kilometres (1.9 sq mi). Swarms can travel up to 800 kilometres (500 mi) tending to move with hot winds and generally towards the coast in most cases.