Dear Readers, I am finding the buddleia outside my office window very distracting, with its red admirals and peacock butterflies and even the hummingbird hawk moths, but today was my first painted lady (Vanessa cardui). Every year I become excited at the prospect of a ‘fall’ of this species – it’s migratory, and its numbers in the UK depend largely on conditions thousands of miles away. The ones in England generally arrive over the Atlas mountains in Morocco, driven ever onwards by the need for food: it’s thought that when the population density reaches a certain level in an area, the adults move on to pastures new, being driven as far north as Orkney and Shetland. This is also the only species of butterfly ever to have been found in Iceland. However, some butterflies make an even longer journey: some butterflies were recently found to have originated in Central Africa, which seems to indicate that the painted lady can make an annual round trip of about 12,000 km.
However, it’s important to note that no individual butterfly makes this whole trip: the butterflies will lay their eggs en route, and the life cycle is a short one, with the process of turning from an egg to an adult taking as little as three weeks depending on temperature and food availability. The caterpillars are fond of thistles, burdock, stinging nettles and viper’s bugloss, and will make a little ‘tent’ out of the leaves to protect themselves. The fully-grown caterpillars are black and spikey, like those of their close relatives the red admiral and the peacock. Sadly, the painted lady cannot survive the winters in the UK and further north in any form, so it’s all a matter of timing.
I remember the great ‘fall’ of painted ladies in 2009 – I was still living in Islingon, but was treasurer for our local community garden, Culpeper Gardens. I popped over, as I did every day, and every single flower and wall seemed to be hosting an painted lady. I had never seen such a concentration of insects of one species in one place, and it felt like one of those miracles that we are blessed with a few times in a lifetime. Often these occurrences are correlated with El Niño years, maybe because the heat dries up the nectar sources in Southern Europe and North Africa, and so the butterflies have to move on, crossing the Mediterranean and the English Channel and flying over the cliffs of Southern England until eventually they end up on some end-of-season buddleia in a North London front garden. Growing a few plants for these wanderers to feed on feels like such a small thing, and it’s so rewarding.
For a very long time, no one could work out whether painted ladies made the journey back south – everyone figured that they probably did (otherwise where would new adults come from every summer?) but we didn’t have the technology to spot them. But in the early 2000s scientist Jason Chapman used a kind of vertical radar to ‘watch the skies’. During the autumn of 2009, Chapman managed to identify the southwards migration of the species at between 200 and 600 metres, using a tailwind to fly at an average speed of 45 km/h. It’s thought that, unlike on the northerly migration where successive generations are involved, on the flight south it’s likely to be done by individual butterflies, meaning that an adult hatched in Scotland could end up migrating some 5000 km south to its final breeding grounds in sub-Saharan Africa. Whoever thought that butterflies were fragile had clearly not met this species. In Martin Warren’s wonderful book ‘Butterflies’, he calls the migration of the painted lady “one of the most outstanding phenomena of the butterfly world…..eclipsing even the famous migration of the Monarch butterfly in North America’.
But how does a newly-emerged painted lady know whether to head further north in search of food, or to hurry south to escape the approaching winter? It’s thought that, even in the chrysalis, the butterfly can detect daylength, which will trigger the general direction in which it flies. Once airborne, the insect can use the time of day and the position of the sun to orientate itself – it uses its antennae to detect daylight, and its eyes to find the sun. On cloudy days, it can use polarised light to detect where the sun is, and they also have a magnetic compass. In order to survive the trip, Monarch butterflies increase in size and fat storage, and a hormone delays the development of eggs, which increases the butterfly’s lifespan, and this may also be the case for Painted Ladies.
Sadly, these finely-tuned creatures with their complicated life cycles are often used at weddings, and released as ‘live confetti’. As you might guess, the idea of releasing live creatures, possibly into an unsuitable environment following a wedding, appals me just about as much as the recent fashion for dyeing doves in different colours and then releasing them for gender-reveals and weddings. Have a bit of respect, people! Animals are not toys.
The caterpillars can also be bought to be reared so that children can understand their life cycles. As far as this goes, wouldn’t it be better to grow caterpillar food plants in the garden, and encourage children to watch them in their natural state? There are plenty of wonders out there, we just have to look for them. Admittedly I’ve sometimes ‘rescued’ caterpillars from areas where they looked to be running out of food or in danger of being strimmed, and it’s fascinating to see them change over time, but I think that’s different from buying in caterpillars for the purpose. Or maybe I’m being unfair. In a way, anything that encourages children to take an interest in the natural world is great, but I think we need to move away from seeing it as a commodity that we can buy, and move towards seeing it as part of our environment, and something that needs to be cherished in situ. What do you think, Readers?