The Purple Hairstreak, Favonius quercus

There is only one brood per year with the adults in flight in July and August. The Butterfly over-winters as an egg. Food plants are Oak trees.

This species is widely distributed across the country but as the adults usually spend much of their time high in trees they are easily overlooked. They are easier to notice when they are on smaller Oaks in open ground as they are over the Railway line at Stour Wood, Wrabness and as I saw them on 19 July 2011 on a hill opposite the visitor centre at Marks Hall, Coggeshall.

My 19 July 2011 visit was at mid day and the butterflies were still for most of the time, between short flights across the same tree. There were about five butterflies in one smallish Oak tree and all looking very worn. Their wings did not open fully as for basking, but only about half way before taking off.

June 2018 was the first time I had seen Purple Hairstreaks in Great Yeldham. They would be seen between 9.00 and 10.00 am on low vegetation in the boggy corner of the paddock. This south-facing area catches the morning sun, ideal for butterflies to warm up at the start of the day. By about 6 pm the summer sun illuminates the more north facing Oak trees in the spinney on the opposite side of the paddock. There the Purple Hairstreaks move about and perch from quite high up to quite low down on their favourite parts of their chosen trees. Other apparently similar trees appear to be ignored.

Weather notes:
2011. July - early August very wet.
2012. April - mid July very wet. August to mid September dry.
2013. Winter wet, March and early April, very cold. The rest of the spring was mostly cold. Early July, v. warm, caterpillars on the nettles. August, warm.
2014. Winter very wet, mild. Spring was early, colder in mid April. Summer to early August, warm without a drought.
2015. Winter normal, March, April - May mostly cold. Sallow flowers opened on March 28 - 29th. Summer, fairly normal.
2016. Winter normal. Sallow flowers opened on April 2 - 3rd. Spring mostly cool and breezy. For a few weeks in late spring there was heavy rainfall and saturated soil and vegetation. Late summer with hot, dry periods.
2017. Winter mildish, hardly any frost. Sallow flowers opened on March 14 - 15th. Warm spells in March. April mostly dry and chilly. First Creeping Thistle flowers open on June 13th, followed by about 7 days of heat wave. Early July was very warm, excellent for counting butterflies. Late summer, autumn normal.
2018. Winter normal with a few days of settled snow. Sallow flowers open on March 26th. March, April mostly cold and wet, May warm. June 11, Bramble flowers opening to greet first Large Skippers. Mid June to early August, very hot and dry. Autumn mostly dry.
2019. Winter normal. Hardly any frost. Sallow flowers seen on March 10th. Spring mostly cool apart from Easter heatwave. May 31, Bramble flowers starting to open. June 1, Buckthorn in full bloom. Dryish summer with some heatwaves.
2020. Mildish winter. Sallow flowers open March 10th. Spring mostly cool. Several warm days in early April and through May. May 28 Bramble flowers opening. Record dry May. June nectar sources mostly Buttercups in the unmown paths, and Brambles.
2021.Winter normal. Very wet, early spring then cold. Sallow flowers opened on March 23rd. Summer with a few hot spells and moderate rain.
2022. Winter, normal. Sallow flowers open on March 18th. Bramble flowers open May 28. Summer, mostly very dry with long hot spells.
2023. Winter normal, some frost. Feb very dry, March very wet. Sallow flowers open on March 21st. Cold wet spring followed by hottest May on record, warm June and wet July. Autumn, mild and wet.
2024. Winter mild and wet. Feb very wet. Sallow flowers open on March 13th.