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A calm, clear morning on Dartmoor and the shallow pools I pass are smooth as glass – scattered wedges of sky reflected between the grass and gorse. I am wandering the western edge of the moor, close to the village of Lydford, best known for its plunging gorge and waterfall. This is a place shaped by rain, from the peat bogs blanketing high ground to the rocky gullies carved by streams.

There are endless puddles and pools, and on this windless day they appear completely flat and still. Only when I look closely, I see that something is agitating the surfaces of the water. Every one of them quivers with life: whirligig beetles.

Small, dark and smooth-backed, these aquatic insects are constantly on the go, spinning around like motorised apple pips. I pause to watch a cluster of a dozen or so. Some slalom left and right through the surface film, paddling their legs and leaving tiny ripples in their wake. Others carve circles on the spot or rotate in pairs as if engaged in a barn dance. Their restless movements, seemingly as random as particles in Brownian motion, are mesmerising.

I wave a hand over them and they respond instantly to the potential threat, gyrating frenetically as if the pool had been heated to a boil. Such hectic activity is believed to bewilder predators.

There are a dozen whirligig species in the UK, although they are hard to tell apart. They are equipped with eyes split into two pairs, enabling them to see both above and below the surface simultaneously as they hunt for prey such as mosquito larvae and invertebrates that fall on to the water. They can also fly to colonise new pools and are widespread.

Whirligig beetles are easy to overlook. But even brief time spent watching these gregarious insects feels like a focus free from other worldly cares. They remind me of sped-up films of traffic or bustling crowds of shoppers – except that their chaotic patterns never wholly make sense. And that is perhaps what is so compelling about them. They invite one to set aside meaning, and appreciate that nature can confound and captivate in equal measure.

• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024, is available now at guardianbookshop.com