Drones are often seen as " layabouts" in the hive .The common description goes something like this: "The drones have a unique purpose in the hive. The drone's primary focus is to mate with the queen. They live in the hive during spring and summer season, where the queen flies to find a mate. Drones also leave the hives to fly in mating swarms where they release pheromones to attract queen bees."
Looks like there is a bit more to drones.
We know that worker bees are deliberately endothermic but workers are not the only ones to generate heat. Drones help maintain nest temperature. Drones stand on or around the brood and also use their flight muscles to generate heat ( Harrison, 1987)
This goes to show that they don't just eat and hope to mate, as is often claimed...and maybe that is not all?
http://link.springer.com/article/10.1007%2FBF00694379#page-1
http://www.tandfonline.com/doi/abs/10.1080/00218839.1965.11100114
http://aesa.oxfordjournals.org/content/64/4/954
http://www.apimondia.com/congresses/2001/Papers/135.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227730/
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0148740
http://www.journals.uchicago.edu/doi/abs/10.1086/284306