I thought I had probably seen my last butterfly of 2016 when I started to put together this collection for 2016 – only to see a peacock flitting around on my lunchtime walk yesterday. Sunny weather or disturbance can bring out some of our hibernating species during the winter so the ‘season’ never truly ends!
Willows (Salix genus) are one of the earliest flowering tree species in the UK and are a fantastic nectar source for early pollinators such as bumblebees and butterflies. These trees are dioecious which means that there are separate male and female trees which can be distinguished by their flowers. Another more commonly known example of a dioecious tree would be the holly – only the female trees bear the red berries. One of the traditional names for willow flowers was ‘vegetable goslings’ which seems a perfect description to me!
The flowers are quite unusual when compared with a simple flower such as a buttercup which follows the classic textbook diagram. Willow flowers are catkins – these are spikes of numerous tiny flowers rather than each catkin representing a single flower. Each of the yellow-tipped spikes in the male flower is one of the stamens and there are generally two or more of these to each individual flower within the catkin – the number varies with species. The same is true, although less easily illustrated, for the female flowers which have two or more stigmas per flower.
The male and female flowers appear at the same time in order that the pollen from the male flowers is able to fertilise the female flowers. The flowers are quite different from one another in appearance and, side by side, it would be easy to assume that a male and a female willow tree were two different species.
The willow flowers are an excellent source of nectar for early pollinating species, such as queen bumblebees which have emerged from hibernation and are establishing nests, or the early Nymphalidae butterflies which hibernate through the winter.
Brimstone butterflies are the perfect harbinger of spring. They are typically the first butterfly seen in most years – excepting the occasional tatty small tortoiseshell or peacocks – and they always look pristine. Perhaps the connection with spring is so strong because they confirm our own perception of the first spring day – they need the warmth and clemency of sun and still blue-skies in February or March to take to the wing.
I saw my first brimstone of 2014 a couple of week ago but they were out in abundance last Sunday – settling on the south-facing hedge in the garden to warm up and bask in the sunshine. A short drive across the Vale of Belvoir saw almost every hedge graced with at least one which bobbed and bounced around the periphery of the foliage.
The brimstone is one of five or six species of butterfly which hibernate in the UK. You may see much tattier and battered small tortoiseshell, comma and peacock butterflies at this time of year along with the occasional clouded yellow and, increasingly, the red admiral. All of these, excepting the brimstone and the clouded yellow, are in the Nymphalidae family – a group which includes many other familiar UK butterflies including the fritillaries and the browns. The brimstone is in the Pieridae family which also includes the whites.
Brimstone butterflies are a single brood species – the adult butterflies emerge in August and are on the wing, feeding and building up fat reserves, until they go into hibernation at the end of autumn. The butterflies, also called imago, re-emerge early in the spring to mate and begin their life cycle once more.
The comma and small tortoiseshell butterflies, in the Nymphalidae family, tend to have two broods in a year – that is the first batch of imago will mate and lay eggs which hatch and give rise to a second batch of imago in the same year. The red admiral has a single brood but the prevalence of imago is affected by migrating butterflies from the continent. The peacock has rather a similar life cycle to the brimstone.
It is always noticeable that the brimstone butterflies look pristine in spring, whereas the commas and small tortoiseshells often look much more battered and tatty. I was hoping this might be explained simply by the Nymphalidae butterflies being older – that is they had been on the wing longer in the previous season before hibernation, but the phenology doesn’t seem to bear this out for all. It could explain the particularly tatty comma and small tortoiseshell butterflies, if some of these are surviving stragglers from the first brood of the previous year.
There is still a difference in family between the brimstone and all of the other hibernating butterflies and I wonder whether the brimstone is simply a more structurally sound butterfly, with stronger wings which are less likely to deteriorate than the other species. The species is the longest living of the UK species, at a year, so the imago would need to be hard-wearing! I would be fascinated to know an answer to this if anybody can advise.
The brimstone butterflies feed on a range of nectar sources – as they are so early to emerge they rely initially upon long-flowering species such as dandelion, or early flowering species such as bluebell, cowslip and primrose. The key food plant in the autumn is thistles with a range of other species also used.
The larval food plant is surprisingly specific and not abundantly common – they require buckthorn or alder buckthorn. The species name for the butterfly eludes to this link – rhamni which refers to the latin for buckthorn – Rhamnus sp. This is a shrub which can be found in hedgerows and woodlands but is not nearly as common as other similar species such as hawthorn or blackthorn. I do not know of any buckthorn in the area but the presence of the brimstone butterflies clearly proves its existence! The comparative scarcity of buckthorn has been directly addressed by Butterfly Conservation in the past with planting programmes to increase their presence within landscapes and this has had a positive effect on the brimstone populations.
The female is much paler than the male – I saw one in the distance on Sunday which I at first through to be a large white until I crept closer and saw the distinctive veined, contoured folded wing which looks so much like a leaf.
The purple emperor (Apatura iris) is not the rarest butterfly in the UK – that rather dubious accolade would go to the high brown fritillary although there are far too many other species, such as the black hairstreak, in close contention.
But the purple emperor is one of the largest and certainly one of the most impressive. It is a woodland butterfly, favouring deciduous woodlands with a dominance of oak or beech although a good supply of willow, the larval foodplant, is another requirement. Perhaps it is this habitat, the high treetops in mature woodland glades, which makes the species all the more regal as it descends and deigns to be appreciated before ascending once more.
They are found in mature woodlands through southern England with occasional colonies elsewhere in the country and, luckily, one of these is only a 40 minute drive from Grantham.
We took a drive down to Fermyn Woods on Saturday, arriving around 10am, and were lucky enough to spot a male purple emperor settled upon a damp digging to the side of the trackway within 100m of the car. The males are seen most frequently as they come to ground to take moisture, nutrients and salts from damp ground and animal droppings – a behaviour which spoils the regal image just a little.
The remainder of the time, the adults spend high in the canopies, feeding upon the aphid honeydew and this is generally where the females will stay – they could be seen occasionally breaking the canopy cover before returning and remaining on high.
The purple emperor is very darkly coloured, almost black, with patterning of white and orange on the top of the wings. The underside are a magnificent rich marbled motif of brown and white, almost as spectacular as the open wings. But when the light catches the wings of the males, the reason for their name becomes apparent as a sheen of purple washes across the wings, marking this out as one of the most spectacular butterflies you are likely to encounter.
As we walked amongst other enthusiasts watching the paths and the canopies, we saw another two in flight, along with many other butterflies including white admirals, ringlets, countless skippers and speckled woods.
The best time to see the purple emperors is around now – the peak date for sightings is given as the 13th July – and they are generally to be found on the ground during the morning when the sun begins to heat through. The ride which runs from east to west through the middle of the woods was the place to be although the woods have a network of paths which are worth exploring for their range of wildflowers including meadowsweet, perforate St John’s wort, hedge woundwort and red campion.