Wild Barcelona: Jewels of summer

You can see them from a distance, glowing like sapphires among the leaves. Their sky-blue iridescence makes the Hoplia coerulea chafers one of Europe’s most beautiful beetles. They do most of their shimmering on vegetation near streams, so to find them in Collserola, head to one of the few places where water flows above ground in summer: the Torrent de Can Codina. In the municipality of Cerdanyola, this tenacious stream eventually works its way to the Besos.

I found a group of males there, positioned conspicuously on the plants, each with a leg or two raised in the air. Passing females, who are a sombre dark grey, with only a faint glimmer of blue, would fly past to inspect the baubles on display and make a selection.

While the beetles wait to be picked out, the proximity of a neighbour can become unbearably irritating. Wrestling matches break out, as rivals grapple and try to lever each other off a leaf. Their hook-like extremities, designed for secure climbing on plants, are useful for slinging round legs and pulling.

Another jewel of summer is the Beautiful Demoiselle (Calopteryx virgo), whose name goes straight to the point. You need to venture further than Collserola to observe them: the fast-flowing streams of Montseny are a perfect habitat. Under the thick July canopy, flashes of metallic turquoise electrify the dappled shade.

Just like the chafers, a male will flaunt his colour to impress a female, who you might mistake for another species of damselfly altogether, given her more subdued coppery-green tones. The male will approach a potential mate and woo her like a peacock. Other damselflies have transparent wings, but those of the male Beautiful Demoiselle are richly pigmented a deep dark blue. The richer the better, instantly read as a sign of physical fitness by the female, as they are spread out before her.