Beetles as Pets?

My students daily bring in beetles to keep in the classroom.  They are getting bigger and bigger.  One day during parent conferences one beetle was chewing the plastic container it was in and escaped somewhere in the classroom.  Students came in every day and looked for it.  We forgot about it and then I moved a chair one time and found it ALIVE.  What it ate we don't know.  But the students were so happy we found it.