Encouraging Common Blue Butterflies

A timely post from a founder member of CMG, Julian:

We’re at that time of year when our upper hay meadow, 800 feet up in North Carmarthenshire, changes daily. Flower heads on the sweet vernal grass develop and extend, golden meadow buttercups appear, white pignut flower heads are focal points. Many more orchids than before are popping up in new places, though some early ones were hit by the mid May frosts. Overall numbers probably haven’t increased that much – several on the steep South slope seem to be struggling to flower, perhaps from the heat and drought? The yellow rattle is widespread but relatively dwarf in most of the field so far, after high germination rates, but poor growing conditions from the last two months of very dry conditions.My favourite hemi parasite meadow plant is lousewort, Pedicularis sylvatica, (below), which flowers early and is such a boon for many bumble bees. The eye is drawn to the pink flowers en masse early on but it’s now drawing to an end. However there’s also much more bird’s-foot trefoil, Lotus corniculatus (BFT) in flower this year than ever before.

All of these plants were introduced as hand collected seed to the meadow over the last 10 years, and it all began with the BFT and yellow rattle. The BFT seed was scattered on this very stony access track margin, below, in full sun, dry conditions, but close to hand to collect seed pods from in subsequent years. The main reason for wanting BFT was that apart from it being a leguminous nitrogen fixer, so natural growth booster for the meadow which hasn’t received any NPK fertiliser or imported muck for over 25 years, it’s also a wonderful nectar source for many insects. Especially B. lapidarius, the Red-tailed bumblebee, below in our meadow, and occasionally honey bees too.

But even more specifically it’s one of the main larval food plants for the Common Blue (CB) Butterfly,  Polyommatus icarus.  Years ago I’d found CB’s on the margin of a local forestry track where BFT grew in similar harsh conditions and a small CB colony existed. I was enthralled by these delicate summer butterflies, and since envied the significant populations at the National Botanic Garden of Wales. The forestry track site was widened a few years back, and the colony destroyed. Apparently last year according to Butterfly Conservation’s annual monitoring, CB population numbers declined by 54 %.

Back in October 2013, click here, I wrote on my own blog about how I’d tried to speed up the process and bought some CB larvae on line, in a very disappointing experience. No adults appeared in the following couple of years as far as I was aware, but more recently I have found the occasional adult in the garden, or meadow.

Two weeks ago, I was therefore delighted to find a pristine and obviously recently emerged adult resting on grass stems in the hay meadow in the early warm evening sunshine.

The following day was even better, and as soon as I walked into the meadow I spotted another on the wing, and then almost immediately the bright blue male chased a female, and I was able to get some pretty good video footage of this mating pair, which stayed bonded, at rest and in flight, for probably nearly an hour.

Subsequently I’ve seen several more on most days in the area of meadow with the most BFT, which I’d concentrated by early seed scattering on a very poor thin soil area of hot South facing bank. So in what’s been a great spring for butterfly flight, I hope that they have the chance to create a viable colony here for years to come. This was another mating pair seen a few days later. Up to 7 have been seen in the meadow at the same time, and around the house where much Black Meddick, BM, Medicago lupulina (I think!) another valued nectar source and also larval food plant, grows. A rather tatty female is shown below feeding from the very small yellow flower clusters of BM …

I also wrote in July 2015 about courtship behaviour in some butterflies in July 2015, click here, but can now add that apparently Common Blues don’t engage in any significant courtship as discussed on the excellent “learnaboutbutterflies” website created by the eminent entomologist and photographer Adrian Hoskins.

Even better I’ve just discovered that an amateur British butterfly fan has very recently published a book reviewing recent research and knowledge of butterfly courtship and behaviour, which sounds like a fascinating, though expensive read – I have a birthday coming soon … Courtship and Mating in Butterflies – 30 Dec. 2019
by Raymond J.C. Cannon (Author).With any luck our adult Common Blues will hang around in the benign weather for another week or two, although I fear that the numbers are already dropping off a little in the heat – perhaps they’ve already quickly done their stuff this year, and have passed the baton on through the next generation of eggs. In a good year in the South of the UK one can expect a second generation of adults to emerge in late July and August from eggs being laid currently by the mated females.

So a very long time after picking those early BFT seedpods, scattering the seeds, and repeating the process over the intervening years, but what a thrill, and enough to persuade me back into the meadow for the odd hour this week collecting both Dog’s Violet and Snakeshead Fritillary seed capsules in what will surely be a year of abundant seed setting for many early flowering meadow plants. After all, for those many plants which just drop, or fling their seeds, even hay making will take a long time to distribute seeds around even a modest sized field. And yes, I’m impatient…

Julian Wormald – June 1st 2020.

3 thoughts on “Encouraging Common Blue Butterflies

  1. Really interesting read Julian. You’ve been seeing similar things to the hay meadows at Waun Las NNR. Many of our earlier flowering orchids have shrivelled up in the heat and dry, most vegetation is very low, including the yellow rattle which already have inflated seed pods. I’ve even found black knapweed and whorled caraway in flower. AND I saw some common blue’s in the new green hay meadows last week for the first time, as well as a green hairstreak, a butterfly I’ve never knowingly seen before.

    Like

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