A device for insertion into an open end of a length of pipe to prevent mosquitoes from entering the pipe is provided. The device includes a piece of flexible foam material having a front face, a rear face and one or more edges joining the front face to the rear face. A plurality of indentions, preferably three, are formed in the front face of the piece of flexible foam material to allow a user to quickly and easily grip the device to insert or remove it from the pipe. The piece of flexible foam material preferably comprises open cell foam sized to permit water to flow through while preventing insects from passing through. The device may be used in connection with a system to prevent mosquitoes from entering into a rain gutter drain extension or a rain barrel system.
