9th October - Portsdown Hill, Hampshire

Over the last few weeks there have been reports of the Long-tailed Blue butterfly having been seen on the southern side of Portsdown Hill above Portsmouth.  With the sun out over the weekend there were several sightings reported with photographs.  Monday presented an opportunity to go, but first thing it was overcast and a little misty, by about 11.00 am the clod started to break up so I headed south in hope I would be able to find at least one.

The Long-tailed Blue is an exotic migrant from the Mediterranean with a handful typically reaching UK shores each year, but experts believe climate change is behind this butterfly reaching our shores more regularly and in vastly increased numbers.

One of the largest migrations took place in 2015 when 60 adult butterflies crossed the Channel in August and laid 1000s of eggs in gardens and allotments along the South Coast.

On reaching the car park there was only one space available.  I walked from the car park to the slope and view point that looked out across Portsmouth Harbour.

It didn't take long to find the spot I had been told to look for them, but with there still plenty of cloud about there was no butterfly action at all.  A message then came in that two Ring Ouzel had been seen around the cliff, so I headed west.  Not having been here before I didn't realise the difficulty there would be in searching the scrub and there was no sign of any thrushes at all.  Walking back the sun was out and it was now quite warm.  A Buzzard and Kestrel flew over and there was a movement now of Red Admiral and a few Large White.

Back at the spot I stopped to talk with someone else who was looking and as we did a blue butterfly flew around by our feet, then settled in the grass.  It was a male Long-tailed Blue.

The butterfly gets its name from the wispy ‘tails’ on the trailing edge of each of its hindwings, which flutter in the breeze. Adjacent eye spots fool birds into thinking this is the head of the butterfly, allowing it to escape any attacks unharmed.  

It then took flight around the area of bramble, it has a jerky and rapid flight that is very similar to a hairstreak, but flies closer to the ground. It is also a strong flyer, borne out by its ability to migrate over large expanses of land and water.

It settled in very much the same area this time on a stem of grass

It made several sorties around the area, but stayed loyal to the grass at the base of the bramble bushes, perching on either the grass stems or the dead foliage.

I was keen to get a view of the underwing, the male has the striking violet-blue colour, while the female is a mix of duller blue and brown. The underside of both sexes is a sandy brown colour crossed by numerous white, wavy lines, very different to the other blues found in this country.

At one point while on one of its sorties it settled on a bramble leaf and drooped the wings down around the leaf.

Back to the usual spot.

Although this species is a rare migrant to the British Isles, it is one of the most-widely distributed Lycaenids in the world, it can be found in Europe, Africa, South and Southeast Asia, and Australia while there are also records of some found in the Hawaiian Islands.  The vast majority of records in the British Isles are from the south of England and the Channel Islands.

When at rest, the butterfly will rotate the hindwings which causes the tails to move, diverting predators from the more-important parts of the body.

There was then a little diversion, one of the visitors spotted these flies in amongst the grass.  They are known as Ectophasia Crassipennis and have only just turned up here in the United Kingdom since 2019, but have distributed widely along the south coast as far as Kent to the east and Cornwall in the west.

They are a species of parasitic fly, that uses several species of shield bugs as hosts for its larvae,  It is seen mostly from August onwards nectaring on flowers.

Close by there was a Cricket, told apart from the grasshopper by the very long antennae.

Close up it is a Short-winged Cone Head, a fairly widespread cricket in southern England found mostly on downland.

Back to the Long-winged Blue, at one point it was thought there were two present but this was not confirmed.  There have been many seen over the last few weeks, with dense areas of Broad-leaved Everlasting-pea (Lathyrus latifolius) along the M27 being considered as suitable breeding sites, the pea being an important larval foodplant as are Bladder-senna (Colutea arborescens) and Broom (Cytisus scoparius).

If the adults arrived in August then it is possible this immaculate individual was one of  possible breeding from those immigrants.  The egg stage lasts around seven to eight days while the caterpillar stage lasts between three and four weeks.  The final Pupa (chrysalis) stage before adult emergence lasts around ten days.

It was reluctant to close the wings so I was grateful to a small breeze that blew the wings up to provide a great view of the under wing.

A welcome addition to my UK list and to that of Hampshire, it takes my UK list to 51 and Hampshire to 47.  It was also the 47th butterfly this year. Still some way to go on the UK butterflies list though.

Before I left I thought it only right to photograph one of the stunning Red Admiral that settled before continuing its flight south.