pts = Flatten[ Table[{{x, y}, Hue[Random[]]}, {x, -1, 1, 0.25}, {y, -1, 1, 0.25}], 1];
StreamPlot[{-y^2, Sin[x]}, {x, -1, 1}, {y, -1, 1}, AspectRatio -> Automatic, StreamPoints -> {pts, Automatic, Scaled[2.3]}, StreamScale -> None, Epilog -> {Blue, PointSize[Medium], Point[pts[[All, 1]]]}, ImageSize -> Large]