Hertfordshire & Middlesex Branch
Saving butterflies, moths and our environment
This part of the website provides information on butterflies reported in the Stevenage area since 1993. The reports are based on records submitted by observers for the area encapsulated in the Ordnance Survey grid reference TL22 10km decad which includes villages Walkern and Great Wymondley, for example. I am most indebted to Andrew Wood, the county butterfly recorder, for supplying the records and a big thank you to all the recorders without which this project would not have been possible. Records for 1993 and 1994 relate to my transect only covering the southern section of Fairlands Valley Park.
Distribution maps are taken from the MapMate database onto which the TL22 data had been applied. The distribution for all species is represented at 2km level (tetrad) as is standard for county distribution maps. Presence of a particular species in a tetrad is dependent on when it was seen since 1995. For the 1995-2009 period presence is denoted by an un-filled diamond; presence during 2010-2019 is represented by a blue square. The darker the blue square the more records submitted and probably increased abundance. Green circles imply that the species was seen since 2019.
Only species which were reported since 1995 and those seen on the Stevenage transect since 1993 are described. The one exception is the Brown Hairstreak, with unconfirmed reports from Norton Green. Species, excluding migrants, not believed to hold colonies in the Stevenage area are highlighted in red on the left.
General Distribution and Status: The current range and status of the species in the UK and how the species has fared in the past. Explanations are given for causes of gains or losses and most are well understood but some are open to conjecture. A brief summary of the state of the butterfly in Hertfordshire and Middlesex is also given. A table is provided for state of distribution and abundance at both national and branch (Hertfordshire and Middlesex) level. An '*' (asterisk) in any entry indicates that not enough data is available to perform the appropriate calculations.
Habitat Requirements: Where the species is likely to be found.
Larval Foodplants: Only the primary foodplants are given here.
Adult Food Sources: The flowers most likely to be visited for nectar for the butterfly. Other food sources like aphid honeydew will also be mentioned.
Historical Records: Records for the Stevenage area prior to Brian Sawford's survey in 1984-86. Any significant records elsewhere in Hertfordshire may also be mentioned.
Local Distribution and Abundance: The state of the butterfly in the Stevenage area (TL22 decad) illustrated by a distribution map. References will be made to tetrads within the TL22 decad. Each tetrad is denoted by a letter, starting with 'A' at the south-western corner, for TL2020 and ending with 'Z' at the north-eastern corner, for TL2828. Presence of a species is indicated by a small dark green circle for 2020 until 2024, blue square (the darker it is the more common) for 2010-19, lavender unfilled diamond for 1995-2009. If a tetrad is blank, then the species has not been reported here since before 1995. The TL22 map courtesy of © OpenStreetMap.
The Records/Abundance chart is only a guide to the number for the associated species found on each sightings report in the area so it is not only transect data (which is the most accurate method of measuring abundance) which is represented. Possible reasons for fluctuations in numbers and changes in range will be explained and are open to conjecture. In most cases they are due to the vagaries of our weather and the quality or quantity of the habitat. The best sites to visit are noted. Weekly totals and phenology charts are shown for the three transects covering Stevenage and Knebworth. A grey square indicates that the transect was not walked in the corresponding week. The highest annual totals are highlighted in yellow and the best weekly counts in orange. Below show the annual transect totals for each species.
Stevenage transect annual totals
Knebworth Park transect annual totals
Knebworth Woods transect annual totals
Life History: A brief summary of the species' life cycle. The earliest and latest records of adult sightings are listed. A phenology chart of the butterfly's flight period(s) covering the transect period from April until the end of September is shown. Week 1 starts on 1 April, week 2 on 8 April and so on until week 26 on 23 September. A phenology chart is shown for records incorporating abundance submitted in the TL22 square since 1995.
Behaviour/Observation Notes: Things to look out for when out in the field and the best times of the day to take close-up photographs. Behaviour of the sexes are different and may be explained here like male territorial activity. Also provided are distinguishing features for look-alike species.
Variations and Aberrations: Any notable variation or aberration worth searching for. Historical sightings relating to Hertfordshire or neighbouring counties are disclosed.
References: Any names highlighted in dark grey in the text will be cited with details listed.
My first experience of a butterfly that I can remember, was as a little boy seeing a Peacock on the lawn in my grandparents' back garden at Bushey Heath in the 1960s. My passion for butterflies has never wavered since then. In the middle of that decade the family moved to Hove and trips to the nearby downs in the following few years yielded many species which I had not seen before like the Chalkhill Blue.
My secondary education was spent at a boarding school near Newbury where I encountered my first Speckled Wood along the country lanes.
After completing my full-time education I moved to Stevenage to embark on my first professional IT job. Although I joined the British Butterfly Conservation Society, as it was then known, in 1973, it wasn't until 1992 when I decided to take butterfly conservation more seriously. In the following year I took on a new transect to record numbers and species of butterflies over a set route, covering Whomerley Wood, Monks Wood, Fairlands Valley Park south of Six Hills Way and Shackledell Grassland. The transect is walked from April to September almost every week so more than 30 years worth of data to work with!
From 2017, transects covering Knebworth Park and Knebworth Woods are walked as well. Ken King walked the Knebworth Park transect between 1996 and 2010.
Since 2004, I paid regular visits to Norton Green especially in high summer to look for the elusive Purple Emperor. It wasn't until 2011 when I finally saw one perched on top of an oak tree west of Watery Grove. Around this time, the beautiful Silver-washed Fritillary was now gracing the common. Since 2012, I have been searching for Brown Hairstreak at the site. Although there are promising signs that it is present there is insufficient evidence to support such a claim.
I must thank Ian Carle, Jenny Oxley, Bob Press and Jo Ward for allowing me to have access to records and collections at the Herts Environmental Records Centre (HERC) at Grebe House, St Albans, Mill Green Museum at Hatfield, Hitchin Museum and Stevenage Museum respectively. I am grateful to Bob Clift for his help and checking these web pages on his Mac.
If you wish to make comments regarding content on the website or anything else please email me.
