Asked by: Katy Williams, Burntwood

Insects have hearts, although nothing like our familiar muscular mammalian hearts. These consist of a narrow tube along the insect’s back that pumps blood (or hemolymph) towards their head. This circulates fluid in an open system with no veins or arteries. The smallest insect is said to be the fairy fly (above), which is a type of wasp that’s less than 0.2 millimetres long. You’d need a microscope to see its heart.

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.