Hygropreference behaviour and humidity detection in the yellow-spined bamboo locust, Ceracris kiangsu

Abstract

Water is a critical resource for all terrestrial insects. The yellow-spined bamboo locust Ceracris kiangsu Tsai (Oedipodidae: Orthoptera), matures, copulates and reproduces in the summer and adults are observed mud-puddling in human urine-contaminated materials on hot days. Besides obtaining NaCl and NH4HCO3, the locust may also compensate for water deficiency. In a dual-choice test in the laboratory, adults prefer to remain on wet rather than dry filter paper at high temperature (36 °C). The females are more likely to move towards and stay on wet filter paper than males. The adults chew wet filter paper in the laboratory at higher temperature and the females consume more than the males. Moreover, foam plastic containing an aqueous solution of an insecticide, bisultap, results in greater mortality in females than a dry formulation, both in the laboratory and the field. The water content of the frass from males is significantly lower than that from females and may partially explain the stronger hygropreference behaviour in females. Other possible reasons for sexually different hygropreference are also discussed. The removal of the adult antennae substantially reduces discrimination between wet and dry filter paper and mortality resulting from wet bisultap formulations in the laboratory. Hence, antennae mediate, at least partially, hygropreference behaviour.