VAL BOURNE’S GARDEN WILDLIFE
We learn more about the hummingbird hawk-moth
WE always expect to see a hummingbird hawkmoth (Macroglossum stellatarum) at the end of October, either feeding on the red valerian (Centranthus ruber) or the late salvias. I haven’t seen one as yet this year, and perhaps I won’t, for it hasn’t been a good year for them here, despite this year’s unusually warm summer.
You may be lucky, though, as hummingbird hawk-moths are very distinctive. They beat their wings 80 times per second, which enables them to hover and, if you’ve good hearing, I’m reliably informed that you can hear a humming sound, although they take their common name from the hummingbird.
I always enjoy seeing these colourful creatures, and they seem to arrive in my garden at teatime so I often watch them. They are considered to be a good omen, because a swarm was seen flying over the English Channel on D-Day on 5 June 1944.
This is fairly standard timing because most of our hummingbird hawk-moths are immigrants from southern Europe and North Africa. Consequently, you’re more likely to see one in southern and eastern England, South Wales and the Midlands, although there are sightings much further north – including the Shetlands. These swarms arrive when warm air floods north from the Continent.
These immigrant moths do lay eggs. Their favoured food plant is lady’s bedstraw (Galium verum), but eggs have also been found on hedge bedstraw (Galium album) and wild madder (Rubia peregrina). Moths have also been seen laying eggs on red valerian, although how successful a food plant this is seems to be unknown.
The green eggs are laid singly on flower buds and they hatch in seven to 14 days, depending on the weather. The green caterpillars can be found from June to October, although I haven’t seen one here. They’re fully grown in 30 days and darken to brown as they mature, before pupating just beneath the soil.
The new adult moth will emerge three weeks later, so some of the hummingbird hawk-moths we see in the second half of summer may well be British-bred. There’s definitely a late-summer peak in numbers.
Some of the adults overwinter in unheated outbuildings, and in crevices and holes in walls and trees, but they only successfully overwinter in mild winters. We had a humdinger of a winter last year and that may explain why we had so few hummingbird hawk-moths this summer.
We still rely on them crossing the Channel, just as they did on D-Day more than 70 years ago, but climate change may favour them in the future.
“Some of the adults overwinter in outbuildings”