Dr. Who: "The bees have gone missing."

In Part one of the Dr. Who season finale this Friday, the only "odd thing that's happened lately," so far as one character can recall, is that all the bees have gone missing. Dr. Who seizes on the information and the Earth (and 27 other planets?) is (or might be) soon saved. I haven't been following the series, so I don't know what this is about — but the reference to honeybee Colony Collapse Disorder and the allusion to Douglas Adams' So Long and Thanks for All the Fish was kind of noteworthy.