Westbury Wildlife

News and information about wildlife in and around the parish.

Westbury Moth, rather than Butterfly, of the week 5th August

   Hummingbird Hawkmoth:  This day flying moth is quite unmistakeable. It has a smart grey brown body with white markings along the sides and orange hind wings. With a 5cm wingspan and its continually whirring wings it makes a characteristic ‘hum’.  Part of its scientific name is Macroglossum which recognises that it has a very long tongue which enables it to collect nectar, while hovering, from long tubular flowers like honeysuckle and red valerian.

 

 

 

 

 

It is a regular immigrant but is now managing to overwinter, especially in the south west of England.  It is a resident moth of Southern Europe and North Africa and is found across Asia as far as China and Japan.  In southern Europe it has two or three generations each year and over-winters as an adult hidden in a crevice.  It is a strong flier and variable numbers come into the UK from France and Spain every summer maybe as early as April but particularly in July and August and lay eggs particularly on lady’s and hedge bedstraws.

Lady’s Bedstraw

The caterpillar is a characteristic green with the hawkmoth spike at the tail end.  These home-produced moths are seen in September and October and an increasing number seem to be over-wintering successfully.  This is another animal we are seeing more of because of global warming.  There is a row for recording this moth on the Westbury Garden butterflies recording sheet.

 

Photos Robert Maxwell Wood   John Ball   Peter Bright

Butterfly of the Week 29th July 2020

Small Copper:  This handsome, brightly copper-coloured, small butterfly lives up to its name.  It is about the same size as a common blue.  It is widely distributed and found in a great variety of habitats across the wider countryside, where its chief food plant – common sorrel grows.  Woodland rides, hedgerows, arable set aside, parks, gardens, and churchyards where it is relatively dry and open, and which contain suitable nectar sources.

 

They are, usually, only a few adults on the wing at the same time in their favoured sites.  They over-winter as caterpillars which go into hibernation by the middle of October.  In the following March, these caterpillars complete their development and pupate in April, after which the first generation emerges in the latter part of May or early June.  The males are territorial chasing away other males and checking out any passing females.  Eggs laid by this first generation, go through to pupate in late June and July such that the second generation emerges at the end of July and into August. These are the butterflies on the wing now.

 

 

A third generation is then produced which emerges in the latter half of September.  It is this third generation, which can appear in large numbers in favourable years, as in Westbury in 2018 after the long hot summer.

 

Photos  Mick Fletcher      John Ball        Peter Bright

Butterfly of the Week 22nd July 2020

Chalkhill Blue:   This elegant butterfly, somewhat larger than the common blue, is confined, as its name suggests, to unfertilised chalk and limestone short grasslands.  Ideally, and perhaps nearly essentially, rabbit grazing to create this short sward height is important.  Certainly, scrubbing up of such habitats, as rabbit numbers have reduced, is connected to reduction in Chalkhill blue numbers.  There may also be climate effects as many populations are struggling, at the moment, across England.  The male is a stunning and unmistakeable milky blue colour while the females are milk chocolate brown.  Both male and female have conspicuous dark lines through the white fringes on edges of the wings that the smaller common blues do not have.  The butterfly is entirely dependent on horseshoe vetch which is, in turn, dependent on suitable grazing to keep the sward relatively short.

Horseshoe vetch flowers obviously in late May but otherwise the fine leaves of the plant are very inconspicuous. The caterpillars are also dependent on attendant ants that they supply with attractive secretions, who, in turn, benefit significantly from these as a food source.  When the butterflies emerge in mid-July and perhaps flying into September the males are particularly conspicuous covering the colony area searching out unmated females.  These females can be inconspicuous but are easily found nectaring on suitable plants such as marjoram and knapweeds and show off the dark lines through the white fringes of their wings.  The eggs are laid on or near the foodplant but seem to fall easily to the ground, where they are invisible in the chalk or limestone rocky soil, and they spend the winter at this stage.   The egg hatches in the following April and the young larvae begin their mutual relationship with the local ants such as the Yellow Meadow ant while feeding on the horseshoe vetch leaves and later flowers.  It is possible that pheromones from ant trails help determine exactly where the female butterflies lay their eggs.  The pupa is formed in June or July and is probably buried by its ant partners that are still collecting its secretions.  Like other Lycaenids the pupa is believed to make ant-attractive sounds!   The single generation is then ready to emerge in late July and onwards.  In Somerset, Chalkhill blues are confined to the Mendips from Wookey Hole Fields to Brean Down and to the reserves on the Poldens.  Most of the sites are in Nature Reserves of one sort or another where suitable grazing can be maintained.  We are fortunate – if you want to see this spectacular, and Near Threatened, butterfly, that Westbury Beacon, Stoke Camp and Draycott Sleights are all good sites even if numbers have fallen in recent years.  They could also be expected on Deerleap and Cook’s field if the food plant survives there as well.  Please let me know if you see any, particularly in out of the way places!

Photos  Peter Bright