Beyond locust color: Disentangling behavior and color traits in desert locust hatchlings

The desert locust, Schistocerca gregaria (Orthoptera: Acrididae), displays a prominent example of phenotypic plasticity in the insect world. An increase in local population density causes shy, sedentary, and cryptic individuals (solitarious phase) to transform into highly active, gregarious, and conspicuous locusts (gregarious phase) that can migrate en masse. These traits fluctuate based on local population density but are also passed down via maternal effects. Typically, isolated females give rise to smaller eggs that result in lighter, green hatchlings, while crowded females produce larger eggs with heavier hatchlings. This plastic effect can be induced by artificially miniaturizing larger gregarious eggs so that they become smaller and give rise to green hatchlings. The association between color and behavior is not as straightforward. To explore this, we conducted behavioral assays on egg-manipulated hatchlings to test whether the changes in body color induced by egg manipulation also affect the behavioral phase.