Pandemonium in the kitchen: “Hummingbird hawk-moth on the salvia!” And there it is, that unmistakable shimmering flight above the patio; the moth’s wingbeats so rapid it appears motionless as it sips from the tubular blooms of Salvia (Amethyst Lips).
It’s only the second time I’ve seen a hummingbird hawk-moth (Macroglossum stellatarum) in our suburban garden. I spotted the first last year, darting from flower to flower in the honeysuckle – another species with long corolla tubes made up of fused petals. The hawk-moth’s choice of tubular flowers is unsurprising, given that Macroglossum means long-tongued. Using its 25-28mm-long proboscis, this formidable day-flying moth can take refreshment from the parts other pollinators cannot reach.
Once the hummingbird hawk-moth has drunk its fill, its spot is taken by a buff-tailed bumblebee (Bombus terrestris) with a problem. Its tongue is only a fifth the length of the hawk-moth’s, so it’s unable to sup from Amethyst Lips by conventional means and must bend the pollination rules. It employs “nectar-robbing”, using its strong mandibles to bite a hole in the side of the corolla tube, through which it steals a drink. By this time of year, almost every salvia sports a tiny puncture wound, a sign of how prevalent this floral larceny is.
I thought nectar-robbing was the buff-tail’s cunning secret, but I’ve learned that it’s just one of a long line of looters – an identity parade that also includes white-tailed and red-tailed bumblebees, as well as some mining and leaf-cutter bees. And that’s not all. The holes made by these primary nectar robbers prove irresistible to species like honeybees and early bumblebees, whose mandibles aren’t always strong enough to bite through petals. Instead, temptation turns them into secondary nectar robbers as they dip in and out of the ready-made holes, bypassing the flower’s reproductive parts that would transfer the pollen during legitimate foraging.
I find it astonishing that plants with long tubular flowers or those with nectar spurs – think comfrey, fuchsia and aquilegia – can produce so many apian villains, all prepared to resort to subterfuge to steal a quick drink. A single patio plant has revealed that, in a bee’s world, length really does matter.
• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 is published by Guardian Faber; order at guardianbookshop.com and get a 15% discount
