D3280: How does marching affect locust carbohydrate and protein consumption?

Exceptional migratory capabilities and a voracious appetite make locusts a daunting threat to food security. Adult migrational flight is known to be energetically costly and fueled by lipid reserves. However, little is known about the energetics of marching locust bands of outbreaking juveniles. In other insects, terrestrial locomotion increases metabolic rates 2–12 times above resting, presumably increasing carbohydrate and/or lipid consumption. We tested how marching affects protein and carbohydrate consumption in nymphs of the African migratory locust (Locusta migratoria), one of the most economically important locust species in Africa, Asia, and Australia. Nymphs marched in a circular arena for five hours daily for three days. Each day after marching, we placed the nymphs in individual cages with two artificial diets with 28p:14c and 7p:35c protein to carbohydrate percentages by dry mass respectively, and measured consumption. All locusts selected carb-based diets during the three days of the experiment. On the first day, the marching locusts ate a significantly higher amount of carbohydrates than the control locusts. Consumption of carbohydrates and protein for day two was not significantly different between the two groups, however marching locusts ate more protein on day three. The lack of a strong and consistent response to marching could be due to the inconsistency in marching among individual locusts. Future studies will explore the effects of marching on macronutrient consumption in other locust species.