How get track of bugs(generated imgs) canvas objs, so actually remove completely from

Basically how or what ways exist, when working in CANVAS HTML5 in javascript or a Library like LimeJs and have a game eg

generate moving bugs randomly that move and disappear by get smaller, and when clicked removed and get points, but if get smaller 0,0 and disappear lost points (removed here too)

how get track of bugs(generated imgs) canvas objs, so actually remove completely from canvas so no spend resources and ram?