Butterfly Conservation
Hertfordshire and Middlesex Target Species Guide 2005

Green Hairstreak (Callophrys rubi)

Green Hairstreak Callophrys rubi © photo: Clive Burrows

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 or Middlesex is either uncertain or declining.

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 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 Highdown near Pirton, the Pegsdon/Telegraph Hills, possibly 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 is a colony on the verge of the A41 near Hemel Hempstead and there have been recent sightings at Blackmore End, near Kimpton and at Crouch End between Langley and Codicote. The known sites actually within Hertfordshire are strictly therefore Highdown, Telegraph Hill, Hexton Chalk Pits, Tring Park and the A41 verge at Hemel Hempstead plus Blackmore End and Crouch End. Hexton © photo: Nigel Agar Table 1: Sites where Green Hairstreak were found 2003 and 2004 (data received by Nigel Agar) Site Tetrad Reference Aldbury Nowers SP9413/SP9513 A41 near Hemel Hempstead TL0505 Tring Park SP930105 Telegraph Hill TL1128 Wood Lane/Pirton area TL1431 Table 2: Sites where Green Hairstreak were found 2001 - 2004 just outside Hertfordshire (these records were reported to the branch website, or known to have been seen) Site Tetrad Reference County 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 Additional information from Upper Thames and Beds & Northants Branches Table 3: Sites where Green Hairstreak were found 1907 - 1995 (data held by North Herts District Council Museums) and supplemented by the most recent branch data (1995-2004) Site Tetrad Ref. Last seen Site Tetrad Ref. Last seen Aldbury Nowers SP91L 2004 Datchworth TL21U 1971 Hudnall Common* TL01B 1936 Bramfield Wood/Forest TL21Y 1970 & 1977 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 2004 Fanshaws TL30J 1955 Deacon Hill TL12J Present Danemead TL30N 1977 Hexton Chalk Pits TL13A 2001 Bayfordbury TL31A 1970 & 1974 Pirton TL13F Present Brights Hill TL32B 1986 Tingley Wood TL13F 2003 St. Johns Wood TL32C 1945 Wood Lane, Pirton TL13F 2004 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 SYMBOL DATE REFERENCE SOURCE 2002-2004 Indicates records sent to Nigel Agar and/or reported to the HMBC Branch Website for the year 2002-2004 O 1995-2001 Indicates 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 O 1970-1987 Indicates records taken from Butterflies of Hertfordshire - Brian Sawford 1987 O 1980-1986 Indicates records taken from Butterflies of the London Area - Colin Plant 1987 O prior to 1970 Indicates records taken from Butterflies of Hertfordshire - Brian Sawford 1987 Records: Please send any records of colonies, singletons or potential sites to: Nigel Agar, 34 Oakfield Avenue, Hitchin, Herts SG4 9JB Telephone: 01462 459870 or Nigel Agar August 2002

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