Bionomics of Austracris guttulosa (Walker) (Orthoptera: Acrididae) During the 1970‐75 Outbreak in Queensland, Australia

Abstract

Studies of Austracris gutrulosa (Walker) showed that oviposition was dispersed and never aggregated and that the nymphs were solitary rather than gregarious. Swarms consisted of overwintering adults in a state of reproductive diapause. Swarms dispersed once sexual maturation commenced in spring. Local and long distance movements resulted in outbreak expansion from arid to coastal and subcoastal districts of Queensland. Parasites, parasitoids and predators are listed and their distribution and effect on locust populations discussed.

Rainfall sequences leading to population increases of Austracris guttulosa (Walker) (Orthoptera: Acrididae) in arid north‐eastern Australia

“…The total population of A. guttulosa increases when 50% or more of the Gulf, Gulf Rivers and arid zone of Queensland receive the initial and two or more follow‐up rains. Only 50% of the area needs to receive rain for there to be overall population increase because: (i) adult A. guttulosa can oviposit five times ( Farrow 1977); (ii) there is little mortality from parasitism in the Gulf and arid zone ( Elder 1997); and (iii) A. guttulosa can move large distances ( Casimir & Edge 1979; Elder 1997) from dry areas into areas which have had rain.…”

“…The distribution of sites receiving rain was then compared visually with maps of the distribution of swarms (≥ 4/m 2 ) or numerous (0.1-3/m 2 ) offspring adults for the following March to September period. March was well past the time when parent adults had died and September was before the major locust movements of spring (Elder 1995(Elder , 1997.…”

“…In tropical northern Australia, a long winter dry season (April to September) is followed by a distinct summer wet season (October to March). Adult A. guttulosa survive the dry season as sexually immature adults, feeding on any source of green food material including the leaves of trees ( Elder 1997). The factors allowing sexual maturation and vitellogenesis are associated with rains early in the summer wet season ( Elder 1995; Hunter 1997).…”

Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview

“…Immature adults form a migrating swarm. The size of a typical swarm can be very large and dense, and it can travel up to 400-500 km in a week [38]. Although adults exhibit impressive migratory swarms, A. guttulosa does not exhibit many traits that are commonly associated with locust phase polyphenism [38].…”

“…The size of a typical swarm can be very large and dense, and it can travel up to 400-500 km in a week [38]. Although adults exhibit impressive migratory swarms, A. guttulosa does not exhibit many traits that are commonly associated with locust phase polyphenism [38]. For example, nymphal color does not become conspicuous upon crowding although densitydependent green/brown polymorphism appears to occur [39], adult morphometric ratios remain constant upon crowding [40], nymphs have never been observed moving in dense bands despite high local densities [38], and oviposition never occurs collectively in egg beds, suggesting the lack of group oviposition [38].…”