White-letter Hairstreak Satyrium w-album

Habitat

The White-letter Hairstreak is found in woodland edges and rides, and sheltered hedgerows. It depends on elm trees and was severely hit by Dutch Elm disease during the 1970's and 80's. Fortunately the caterpillars have been found to survive on new sucker re-growth as well as fully mature trees, and populations have now recovered in many places, although it is still cause for concern. Today it is fairly widespread and locally common throughout most of England, and its range has been extending northwards. Like the Purple Hairstreak it spends most of its time at high level feeding on honeydew, but will come down to nectar on flowers during early morning and late afternoon.

Identification

Both sexes are similar with a distinctive white 'W' on the dull brownish-grey underside of the hindwings. It may be confused with the Black Hairstreak, which has a brighter band of orange and a row of black spots along its inner edge.

Flight times

The White-letter Hairstreak is single brooded and overwinter as eggs, with adults on the wing during July and August.

Food plants

Eggs are laid on a variety of elm species.

White-letter Hairstreak
White-letter Hairstreak - © Simon Jenkins

Distribution Maps

2005-2009
White-letter Hairstreak distribution map 2005-09
2010-14
White-letter Hairstreak distribution map 2010-14
2015-19
White-letter Hairstreak distribution map 2015-19
2005-2019
White-letter Hairstreak distribution map 2005-19

Some areas show losses, particularly in Nottinghamshire and the eastern half of Leicestershire. It will be interesting to note whether the planting of disease-resistant elms will see an increase in the future.

2015
White-letter Hairstreak distribution map 2015
2015 Summary
No of tetrads 65
First sighting 10/05/2015
Last sighting 23/08/2015
2016
White-letter Hairstreak distribution map 2016
2016 Summary
No of tetrads 51
First sighting 22/06/2016
Last sighting 31/08/2016
2017
White-letter Hairstreak distribution map 2017
2017 Summary
No of tetrads 58
First sighting 31/05/2017
Last sighting 17/08/2017
2018
White-letter Hairstreak distribution map 2018
2018 Summary
No of tetrads 100
First sighting 10/06/2018
Last sighting 31/08/2018
2019
White-letter Hairstreak distribution map 2019
2019 Summary
No of tetrads 56
First sighting 22/07/2019
Last sighting 26/08/2019

Photo Gallery


Similar or Easily Confused Species and ID Hints

Green Hairstreak Callophrys rubi

Old and overmature Green Hairstreak can loose much of their green colouration, leaving only a dull brown. This can cause confusiton with other small brown butterflies.

Green Hairstreak
A worn Green Hairstreak lacking most of it's green colouration - © Simon Jenkins