Target Green Hairstreak - Herts & Middx Butterfly Conservation

Target Species ~ Green Hairstreak (Callophrys rubi)


Green Hairstreak
Green Hairstreak
Callophrys rubi
© photo: Trevor Chapman
Status

The Green Hairstreak is identified in the Thames Regional Action Plan as having Low Priority status There is no Species Action Plan available at present. Although identified as "Low Priority" the Green Hairstreak has been identified as a species whose status in Hertfordshire is uncertain and the species has shown significant recent declines. It is absent from Middlesex.

Behaviour and Identification

The Green Hairstreak, like most of its family, is a small butterfly whose adults fly once during the year and it is normally confined to small colonies. It is therefore a rather elusive species, often said to be difficult to see, but by hairstreak standards is quite distinctive when seen if only because it flies at a low level. The characteristic green-and-chocolate brown flickering flight is unmistakable. As it always perches with the wings closed, the green underside of the wings are visible and distinctive being of a shade of pale, slightly bluish green not often found in nature and certainly in no other British butterfly.

Individuals are usually seen in one of two possible modes. The first sightings of the season are of displaying males high in the bushes. Later sightings are usually the females flying low in search of egg laying sites usually on Rockrose but also, it has been seen to lay on Dogwood, Buckthorn, Bird's-foot trefoil, Bramble and even Cross Leaved Heath. There may be other foodplants.


Dogwood in autumn
A view of Birds-foot Trefoil
Rock Rose

Dogwood in autumn
cornus sanguinea
© photo: Malcolm Storey
BioImages - Virtual Field-Guide (UK)
Common Bird's-foot Trefoil
lotus corniculatus
© photo: Malcolm Storey

BioImages - Virtual Field-Guide (UK)
Rock Rose
helianthemum nummularium
© photo: Nigel Agar


Flight Period and Life History

The caterpillars are green and inconspicuous. It is the only British hairstreak that over-winters as a pupa. Pupation seems to be dependent on ants. The pupae, which can emit a distinct squeak, have been found in ants’ nests. The first sign of the adults in late April or early May, are of displaying males, possibly accompanied by females, high in hedges or on individual bushes, perched on leaves and periodically flying up to engage in aerial dogfights with rivals. Later, the females fly low over the low herbage and chalk grassland turf in search of an egg laying site. The flight period is normally from April to June peaking in mid May. It is therefore the earliest of the British hairstreaks and the discovery of a colony can be the first butterfly treat of the year. There is the possibility that there might be a 2nd brood in July or August as fresh individuals seen flying very late have been reported from Dorset. (Reference: British Wildlife 14/1 October 2002 page 56)

Habitats

The habitat must therefore contain both grassland and scrub. A restricting factor may be the existence of short well-cropped turf with well-established ant hills. Long unkempt grass can be unsuitable for ants and this breaks a chain in the habitat requirements for the hairstreaks. The catholic choice of food plant means that the Green Hairstreak can form colonies in a variety of habitats although in Hertfordshire, at present most known colonies are on the high chalk of the Chiltern ridge. One accidental result of this preference is that many Hertfordshire colonies straddle the borders with either Bedfordshire or Buckinghamshire which has the effect of distorting the records.


Hexton Chalk Pit
© photo: Nigel Agar


Green Hairsteaks form small and discrete colonies which are sometimes scattered over a fairly wide area of a suitable habitat. They can almost certainly move through unsuitable habitat to establish new colonies. On the Telegraph/Pegsdon Hills for example a colony faithful to the lynchet area on Noon Hill failed to appear one year but a colony appeared on the other side of the Pegsdon Barns valley above a disused chalk pit. Both are on the Bedfordshire side. Sometimes the butterflies appear in the gullies on the top of Telegraph Hill and in the scrubby area known as Hoo Bit (in which case they count as Hertfordshire insects!) These locations are scattered on either side of the Beds/Herts border which can make the county records quite variable. A local extinction anywhere should not be assumed without an extensive search of nearby locations.


Pegsdon Hills
© photo: Nigel Agar

Distribution in Hertfordshire and Middlesex

At present, active known colonies along the Chiltern tops are the Wood Lane area near Pirton, the Pegsdon/Telegraph Hills, occasionally at Hexton Chalk Pits, the Barton Hills, Sharpenhoe Clappers, possibly the Sundon Downs then, to the west of the Luton-Dunstable conurbation, are sites along the Whipsnade escarpment, at Ivinghoe Beacon/Ashridge, Aldbury Nowers and finally Tring Park.

Off the Chilterns, there was a colony on the verge of the A41 near Hemel Hempstead but there have been no recent sightings nor at Blackmore End, near Kimpton or Crouch End between Langley and Codicote. The known sites actually within Hertfordshire are strictly therefore the Wood Lane area near Pirton, Telegraph Hill, Hexton Chalk Pits, Tring Park and Aldbury Nowers.



Hexton
© photo: Nigel Agar

Table 1: Sites where Green Hairstreak have been found since 2007

Site Tetrad Reference
Aldbury Nowers SP9413/SP9513
Tring Park SP930105
Hexton Chalk Pit TL1029
Telegraph Hill TL1128
Wood Lane/Pirton area TL1431


Table 2: Sites where Green Hairstreak have been found just outside Hertfordshire

Site Tetrad Reference County
Pegsdon Hills area TL1229 Bedfordshire
Sharpenhoe Clappers TL064296 Bedfordshire
Whipsnade SP999185 Bedfordshire
Barton Hills TL095295 Bedfordshire
Ivinghoe Beacon SP961163 Buckinghamshire
College Lake (Tring) SP933140 Buckinghamshire
Pitstone Hill (next to Aldbury Nowers) SP950143 Buckinghamshire


Historic distribution
Table 3: Sites where Green Hairstreak were found 1907 - 1995 (data held by North Herts District Council Museums)
Site Tetrad Ref. Last seen Site Tetrad Ref. Last seen
Aldbury Nowers SP91L Still present Datchworth TL21U 1971
Hudnall Common* TL01B 1936 Bramfield Wood/Forest TL21Y
Bricket Wood TL10F 1907 Knebworth Woods TL22G 1922
Symondshyde TL11V 1951 Graveley TL22I 1948
Wheathampstead TL11W 1986 Little Woods TL22X 1941
Lamer Park TL11Y 1979 Weston Hills TL23L 1979
Ravensburgh Castle TL02Z 1985 Weston TL23Q 1986
Noon Hill TL12E Present Cuffley Station TL30A 1972
Telegraph Hill TL12J Still present Fanshaws TL30J 1955
Deacon Hill TL12J Still present Danemead TL30N 1977
Hexton Chalk Pits TL13A Still present Bayfordbury TL31A 1970 & 1974
Pirton TL13F Still present Brights Hill TL32B 1986
Tingley Wood TL13F N/A St. Johns Wood TL32C 1945
Wood Lane area, Pirton TL13F Still present Green Tye TL41P 1976
Dell, Cuffley* TL20F 1965 Stocking Plantation TL42K 1942
Essendon TL20T 1938 Long Meadow TL42Q 1942
Lemsford Springs TL21G 1979 Whippendell Woods TQ09T 1979
Digswell TL21H 1961 Oxhey Woods TQ19B 1907
Mardley Heath TL21N 1986


Distribution Map of Green Hairstreak in Hertfordshire and Middlesex

Click on map for details

Green Hairstreak Distribution map in Hertfordshire and Middlesex


SYMBOLDATEREFERENCE SOURCE
2002-2004Indicates records sent to Nigel Agar and/or reported to the HMBC Branch Website for the year 2002-2004
O1995-2001Indicates records taken from the Herts & Middx Butterfly Report for 1999 - John B. Murray & Rob Souter and Herts & Middx Butterfly Report for 2001 - John B. Murray & Andrew Wood
O1970-1987Indicates records taken from Butterflies of Hertfordshire - Brian Sawford 1987
O1980-1986Indicates records taken from Butterflies of the London Area - Colin Plant 1987
Oprior to 1970Indicates records taken from Butterflies of Hertfordshire - Brian Sawford 1987