The invasion of the Red Admirals
Last weekend was warm and calm and we had an invasion of Red Admiral butterflies (Vanessa Atalanta) in our backyard. They were very likely lured here by following the sweet smell of ripe plums, of which some were even starting to ferment.
Feasting on fermented fruit can make them tipsy and some of them had clearly lost some inhibitions. It was easier to get close - and when they were resting they were surprising stationary. Some even landed on me; it is both fascinating and frustrating to have butterfly land on the hand that holds the camera!
And they were all over the place. Most were crawling around in the grass from plum to plum, but they were also in the trees around the plum tree, resting, and even on my flag pole. There were so many that I couldn't count them, but I'd say at least 50, probably more.
It is quite common from Red Admirals to swarm on ripe plums and other fruits. Or the sap of wounded trees. Still it was the first time I have seen them in such numbers in my garden, which probably it due to our plums being especially abundant this year and the calm, warm day being a weekend and not a weekday, so I was there to see it happen.
The reason why they are so active eating right now, is that they are migratory. They are very strong flyers that can fly up to 36 hours in one go. And they migrate to south of the Alps in order to mate there and lay the foundation for the Admirals flying in next year. Next years butterflies will mate here and lay eggs, mainly on nettles. If winds are favorable they can reach the Alps in 2-3 days, though normally it is a trip taking up to two weeks.
In Denmark those few that stay will not survive the winter. They do not have the trait of other Nymphalidae (danish: takvinger) to seek out cracks and chinks, but try to weather it out on branches or fallen leaves. And if the winter doesn't get them, old age will.
Sugar has half the energy per unit of weight compared to fat, so they will not be able to use it immediately. Still they do need a lot of sugar and that is why they are so attracted to ripe fruits and to the butterfly bush (Buddleja) in the late summer and early fall.
In Danish (and I think this goes for the other Scandinavian languages as well) the Red Admiral is plainly referred to as an Admiral. We do have the term "Hvid Admiral" (White Admiral) but that is another butterfly (the Limenitis Camilla). In English it is also know as the Red Admirable, which turns out to be much more correct, because the name is derived from the Latin word "ammirabilis". So while their name often is justified by referring to the uniform of an Admiral, and while they are strong enough flier to cross the seas even to isles in the North Atlantic, this is not the original meaning of the name.
And apparently in the dark ages, where superstition was much more widespread, their black wings with blood-red markings and white stripes got them associated with the Devil and made them harbingers of death and ill tidings. Much like black cats to some degree are today, I guess. So much for being admirable...