send wordpress ajax with form serialize

ajaxformserialize.php

$(".mgm-ajax-form").on("submit", function(e){
        e.preventDefault();
        var form = $(this);
        ajax$.ajax({
            action: "mgm_insert_marker", 
            type: "post",
            url: ajaxurl,
            data: form.serialize(),
            //_ajax_nonce: $("#_wpnonce").val(),
            beforeSend: function(){
                $("#loading").appendTo("#load").fadeIn("fast");
                $("#formstatus").fadeOut("slow");
            },
            success: function(html){ 
                $("#loading").appendTo("#load").fadeOut("slow");
                $("#formstatus").html(html).fadeIn("fast"); 
            },
            error: function(xhr){
                console.log("Error: " + xhr.responseCode);
            }                
        }); 
        //return false;
    });