Alatae production in the cereal aphid Sitobion avenae

Crowding of L₃, L₄ and apterous adults ofSitobion avenae results in an increase in production of alate offspring. Crowding of L₁ and L₂ results in a slight increase in their number becoming alatae. Fewer alatae are produced by apterae on ears before and during flowering than in later ear developmental stages or on seedling leaves. On ears before and during flowering reproduction was higher than on the leaves and later ear growth stages. Brown forms often produce alatae less readily than green forms.