I came across this idea and I think this would be a hit with your art students. Watercolors and doodling and bugs - a little bit of fun for everyone. You can create it as a simple line drawing or you can you a pen and ink project. Simply doodling and add color when time permits is one way to make this move from a 30 minute project to a series on bugs.
Here is a video of my firebugs projects - feel free to add this to your series: