What is it with tennis drills and caterpillars? There are at least a couple more caterpillar-named activities in this blog if you have the time to search for them. This one I stole from Tedi Doncheva, a pro at Rock Hill Tennis Center in Rock Hill, SC. Thanks, Tedi! Good for any beginners working on their volley shot.
Place several spots in a diagonal line near the net. First spot should be closest to net; last spot should be across court, at a spot farthest back from net where player may be likely to hit a volley. All spots should be in front of service line.
Closest spot is designated caterpillar's tail. Farthest spot is caterpillar's head. Players begin at closest spot. If they hit volley safely into play, they advance one spot. If they miss, they go back to tail spot. Goal is to be first player to advance from tail to head. Once this is accomplished by someone, rearrange spots so that they are running the opposite direction on the court. So for example if the 'tail' was closest to net on deuce side of court and 'head' was near service line on ad side, rearrange so that 'tail' is now closest to net on ad side and 'head' is now near deuce side service line.
After two rounds of all players hitting volleys, consider having at least one player on the other side of the net attempting to return any of the volleys hit by the caterpillar players.