When I am relieving for a teacher who is ill, one of my favourite days is to (with permission) disregard whatever the kids are usually doing, and spend the whole day studying Dung Beetles. The kids enjoy ewwwing over the name in the introductory talk, but almost always get very interested, very rapidly, in this wonderful and useful species of insect.
I set up 10 or so different teaching stations around the room, covering topics like:
Dung Beetle lifecycle
Dung Beetles in Ancient Egypt (Scarab worship, hieroglyphics, lapis lazuli etc.)
Dung Beetle maths (a series of problems involving problems like distance of rolling dung-balls of a certain circumference, given a certain speed etc...)
Dung Beetle Art (colours, iridescence, blending colours and colour mixing, stone door-stop scarab painting etc.)
Dung Beetle physiology (name the parts, what use are the elytra, How can you tell a dung-beetle from other beetles etc.)
English essay: "Why are Dung Beetles so important?" Or "Why I like/ don't like/am indifferent towards dung beetles"
Dung Beetles Interesting Facts Quiz (Do Dung Beetles have poo preferences? Where are dung beetles found? What do dung beetles do with all their dung? Are dung beetles good or bad parents? etc.)
At lunchtimes, I've often had to prise kids away from their projects and banish them outside to have their lunch.