[]Uncaught TypeError: Cannot read property 'XXX' of undefined

private var spe:Sprite;
private function showApe():void {
            spe = new Sprite();
            spe.mouseEnabled = true;
            spe.x = 100;
            spe.y = 100;
            spe.width = 512;
            spe.height = 512;
            spe.size(512, 512);
            Laya.stage.addChild(spe);
            spe.graphics.drawRect(0, 0, 515, 515, "#996633", "#333333");
            spe.on(Event.MOUSE_DOWN, spe, onMouseDown);
            Laya.stage.on(Event.MOUSE_UP, this, onMouseUp);
            Laya.stage.on(Event.MOUSE_OUT, this, onMouseUp);
  }
private function onMouseDown(e:Event):void {
            spe.startDrag(new Rectangle(0,0,800,800));
}
鼠标点击Sprite报错：
Uncaught TypeError: Cannot read property 'startDrag' of undefined