A trigonometric approximation was used to describe the head shape of common vegetable-feeding aphids, Aphis gossypii Glover, Aulacorthum solani (Kaltenbach), Brevicoryne brassicae $(Linnacute{e})$, Macrosiphum euphorbiae (Thomas), and Myzus persicae (Sulzer). After acquiring and standardizing digital images of the alate aphids, a frontal curve was represented as a set of points in a given domain, $-pi/2leqchileqpi/2$. Then, the points were approximated by the function, $y=a_0+sum^{45}_{n=1}(a_{2n-1}cos(2n-1)x+a_{2n};sin;2nx)pi$. Coefficients of the function were calculated by multiple regression analysis, and the averages of coefficients were used to reconstruct the generalized shape of each species.