Observations on the biology of some morabine grasshoppers

Abstract

The Morabinae of Australia (0rthoptera : Eumastacidae) include species which come to maturity in the winter and those which do so in the summer; both have high threshold temperatures for development. For complete development nymphs of "winter" species require temperatures above 24°C in the later instars of the females, but "summer" species require high temperatures at all stages and in both sexes. The eggs require about 7 days of moisture and will then hatch, even if in dry sand, in about 30 days at 30-35°C; only the eggs of winter species will hatch at temperatures below 25°C. The eggs lose negligible amounts of water once partly developed. Water is absorbed until the weight of the egg is about doubled, but saline water is lethal above about 2% salt concentration and sublethal concentrations delay absorption of water. Adults rarely reach population densities greater than one morabine per square metre. The adults are long-lived, up to 16 weeks in the field and 30 weeks in the laboratory, and may move as much as 5 m in a week. Morabines have an annual life cycle with no true diapause. The eggs of some species may spend up to 6 months in the soil.