When I took a course on queen rearing, we used a Chines grafting tool. The tool, as it was picking up the "invisible" larva at the same time, picked up the royal jelly, no need to prime the cell, devices (whatever they are) would no doubt have enough royal jelly on it to keep that larva alive, until it is fed more. As Michael said, if you can see the larva, it is too old. Look for cells that all you can see is the milky looking royal jelly and take that, that would be a larva that is under 36 hours old. The younger the larva the better the end result will be. Have that beautiful, most wonderful day, health and life. Cindi