Visiting a plague of locusts on your enemy was once the most terrible curse imaginable, and your only hope was that the `plague' might not be interested in your crop. Some locust species specialise in devouring specific plants,while others will consume anything in their path. The driving forces behind insects' food preferences intrigue David Raubenheimer and Steve Simpson, and they wanted to identify `the factors that underlie the dietary breath of locusts' explains Raubenheimer. The team chose two species of locust with very different preferences, to test their dietary requirements. Locusta migratoria survives on a restricted diet eating grass alone, while Schistocerca gregaria consumes most any plant it comes across. Raubenheimer and Simpson offered both species a high protein dish and a low protein diet, and found that given the choice, Schistocerca consumed slightly more protein than the fussier Locusta. On testing how the insects faired when fed imbalanced diets, the team discovered that Schistocerca was able to make the most of the high-protein diet, by ingesting more protein as well as using the excess to supplement its energy demands when carbohydrates were scarce(p. 1669). So, it's little wonder that the flexible Schistocerca is the locust of biblical fame.

Raubenheimer, D. and Simpson, S. J. (
). Nutrient balancing in grasshoppers: behavioural and physiological correlates of dietary breadth.
J. Exp. Biol.