Small Skipper

Thymelicus sylvestris

General Distribution and Status

The Small Skipper is widespread and common in England and Wales. It is slowly expanding northwards and reached east Scotland south of the River Tay since the turn of the century. Although there has been a significant decline in numbers since 1976 there was a slight increase since 2009 (Brereton et al.) in spite of poor seasons since 2015. In Hertfordshire and Middlesex, no general increase is apparent and since 2006 numbers have fallen quite dramatically although distribution is relatively constant (Wood, 2016) although now the species appears to have disappeared in many parts of north-east Hertfordshire (Wood, 2020). It is possible that more Essex Skippers are counted instead as more observers are aware of the differences between the two species. Another possible reason for the fall in numbers is the application of neonicotinoid pesticides on field margins where wild flowers and larval foodplants can absorb chemicals adversely impacting insects including butterflies (Gilburn et al.).

UK distribution map
UKBMS Species summary (2020)

Habitat Requirements

Rough grassland, where grasses are left to grow, in fields, roadside verges and edges of woodland.

Larval Foodplants

Yorkshire Fog Holcus lanatus but Timothy Phleum pratense, Creeping Soft-grass Holcus mollis and False Brome Brachypodium sylvaticum are also occasionally taken.

Adult Food Sources

Thistle Cirsium sp. (430), Common Bird's-foot Trefoil Lotus corniculatus (374), Common Knapweed Centaurea nigra (225).

Historical Records

According to Gibbs' survey in 1902, Matthews reported seeing the species at Norton Green Woods. It was probably common all through the 20th century as there are no reports of absence or reduction in numbers during most of this time. For example, Bell reports in his 1973-76 survey that it was 'locally abundant'. However, the Gladwins' article on their Digswell garden butterflies between 1970 and 2001 noted that it was 'once common, now regular in very small and declining numbers' which reflects the situation in the UK as a whole at least since 1976 (Fox et al.).

Local Distribution and Abundance

The map indicates that the species is well distributed in the area. As noted above, although numbers have fallen the butterfly was found in two new tetrads for the first time since 1995 in 2016 - TL22H (north-west Stevenage) and TL22J (north of Graveley). However, there are still a few tetrads where no sightings have been reported since 2009 (the unfilled 'diamonds') which is probably because of inferior recorder effort. Sightings were reported from TL22C (fields between Norton Green and Almshoebury) on 3 August 2021 and TL22W (near Benington) on 22 July 2021, the first records in these tetrads since at least before 2010. Fairlands Valley Park, Great Ashby Park and Knebworth Park are the best places to find this species. There has been an alarming decline since 2015 with 2018 probably the worst on record since the start of the survey. The cold weather in early spring may have decelerated development of the larvae increasing the probability of being predated by birds. There was a small increase in abundance in 2019 but fell back slightly in 2020 and even further back in 2021. 2022 saw a slight recovery and the flight season ended earlier than usual. Two specimens were seen at Weston Park (TL22P) on 4 July 2022 - first records in this tetrad since the 1995-2009 period. Although the Small Skipper was more common in 2023 when it appeared numbers markedly dropped by the end of July. One observer who undertook a walk around Langley on 8 July 2023 counted 13 specimens - first records in TL22B since the 1995-2009 period.

Transect weekly counts

Stevenage (South Fairlands Valley Park) transect 1993-2023

A fluctuating picture is probably a result of the species' sensitivity to changes of habitat or cutting regime on grassy areas. Numbers show a slight decline in contrast to a significant one across the county and the increase since 2012 is probably attributable to selective cutting on Shackledell Grassland. One example of the butterfly's varying abundance is in 2001 when only 19 specimens were counted for the whole year compared to an estimate of 500 on one July day at Knebworth Park. Perhaps this indicates that climate is not as important a factor on the insect's abundance as other species although the warm and dry springs or early summers of 2017-2022 seem to have had a damaging impact on abundance in these years. Did some larvae starve in the dry conditions?

Knebworth Park transect 1996-2010 and 2017-2023

Like the Essex Skipper this species has suffered a huge decline since 2005 when 451 were counted. In 2010 only two were recorded and 72 in 2017-2022 altogether. Habitat loss or change is likely to be one of the main reasons although warm and dry weather in the spring or early summer may have had an impact on abundance as indicated for the Stevenage transect.

Knebworth Woods transect 2017-2023

Low numbers in the five years of the survey. All were seen in grassy areas like Burleigh Meadow and Norton Green Common.

Pryor's Wood transect 2000-2022

Several were seen in most years in the 2000s with a best count of seven on 24 July 2008 but between 2008 and 2019 only two known records were submitted, on 9 August 2015 and 22 July 2019 (three specimens) although there was a possible example in 2017. However, there were four reports received for 2020 including a total of seven specimens on 26 June but no records were submitted in 2021 and 2022.

Life History

Earliest date: 6 June 2015 at GlaxoSmithKline, Stevenage
Latest date: 22 August at Fairlands Valley Park in 2012 and at Norton Green Common in 2015

There is only one generation of this butterfly with the vast majority on the wing in July although some will linger beyond the middle of August. Several eggs are laid in the sheaths of grasses. I saw a female egg-laying on Yorkshire Fog at Norton Green Common on 16 July 2019 at 6.15 pm. The larvae on emerging construct a silk cocoon still within the sheath of grass and hibernate in this chamber. In the following spring the larvae emerge from the cocoons and feed on the grass blades. When fully grown, a tent is spun using the grass blades within which a pupa is formed.
More details on the UK Butterflies website

Behaviour/Observation notes

Because of the confusion between this species and the Essex Skipper the best time to positively identify which one is either in cloudy weather or in the evening when the butterflies are less active. Early in the morning is also another good time to look for these skippers as they are often found feeding on flower-heads (Riley). Approaching them at rest or feeding should then be far easier to get close-up views of the antennae, a distinguishing feature. Differences are explained in the account for the Essex Skipper.

Variations/Aberrations

Varieties or aberrations of the Small Skipper are rare. A specimen with its ground colour very pale white is ab. pallida was spotted in Scotland in 2010.
Find out more on the UK Butterflies website