Country diary: Its a summer of love for the red soldier beetle

Hayling Billy trail, Havant, Hampshire: These striking insects are clearly enjoying the heat – but there’s only so much of it they can stand

It’s hot and humid, and without even a whisper of a breeze to temper the heat, the short walk into town feels like an effort. I’m not the only one struggling with the extreme temperature. Bumblebees usually throng the feral buddleia bushes and clumps of red dead-nettle that grow along the path, but today they’re conspicuous by their absence – their furry bodies make them susceptible to heat exhaustion and unable to forage or fly. The gregarious flocks of house sparrows that inhabit the hedgerows have fallen silent, two carrion crows are paddling listlessly in the shallows of the Lymbourne stream and a young blackbird lies prone on the path, wings splayed, head cocked and panting.

But some like it hot. A stand of common hogweed is swarming with hundreds of common red soldier beetles (Rhagonycha fulva). These soft-bodied leatherwings are so-called as their orangey-red and black colouration is reminiscent of the red-coated uniform of the British army, but these insects prefer to make love, not war. They dedicate a significant proportion of their short lives to mating and are more popularly known as hogweed bonking beetles. True to form, pairs of insects cover the mattress-like umbels of white flowers, the smaller males piggybacking their paramours. A few females are attempting to shake off their suitors, curling their abdomens to avoid genital contact, but most couples are copulating.

As cold-blooded creatures, a whole range of their biological functions is affected by changes in their thermal environment. Beetle reproductive rates typically increase when the temperature rises, but heat stress can have a significant impact on fertility. Research shows that heatwave conditions can damage male beetle reproduction, reducing sperm production, viability and migration through the female reproductive tract, and that exposure to successive heatwaves can leave males virtually sterile.

A more recent study suggests that beetles have sophisticated mechanisms that potentially allow them to cope with temperature fluctuations. But with the climate crisis driving extreme weather events and scientists predicting that UK summer temperatures could regularly reach or exceed 40C, only time will tell whether a summer of love will continue to perpetuate the species.

Country Diary is on Twitter at @gdncountrydiary

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