Speckled Wood (Early Stages)

[Vince Massimo]

This butterfly is seen in a variety of habitats, including gardens, but is at its best in dappled woodland clearings where males are often seen endlessly sparring for territory. The fact that this is the only species in the British Isles which can overwinter as both a larva or pupa, results in a series of overlapping generations throughout the following season. As such, adults can be seen anytime from early March through to early November. My latest personal sighting was on 25th November 2021 in Crawley, Sussex and my earliest on 24th February 2019 at Ferring Rife on the Sussex coast.

There are a number of sub-species, but this report relates to ssp.tircis in its southerly range.

The primary larval food plants are grasses like Cock’s-foot (Dactylis glomerata), Common Couch (Elytrigia repens), False Broome (Brachypodium sylvaticum) and Yorkshire-fog (Holcus lanatus).

THE EGG AND LARVA

It was commonly thought that eggs were laid singly, but from personal observations, they are also sometimes laid in pairs on plants that vary in location from deep shade to more open positions. In Crawley, Sussex on 24th April 2009, I watched as a female oviposited on the underside of a blade of grass. She visited three different clumps, which were in full sun, and on each occasion laid a pair of eggs rather than the usual singleton. I observed another pair of eggs being laid in a shady location in Woldingham, Surrey on 13th June 2010 and again at Gatwick, Sussex on 30th April 2019.

Pair of Speckled Wood eggs - Crawley, Sussex 24-April-2009

On 25th May 2014 I rescued an egg laid in a semi-open location on a grass verge. Two further eggs laid in a shady position under a tree were rescued from the council strimmer on 13th June 2014. Then, on 23rd July 2014 a female laid an egg in my Crawley garden on a plant which was in permanent deep shade.

Fresh Speckled Wood egg - Crawley, Sussex 25-May-2014

Fresh Speckled Wood egg - Crawley, Sussex 13-June-2014

Typically, an egg will hatch after 7-10 days, after developing a dark spot at its apex. This is the head of the developing larva which becomes visible through the transparent eggshell.

Speckled Wood egg (4 hours before hatching) - Crawley, Sussex 19-June-2014

Of the four larva reared, one consumed the empty eggshell upon emerging and one did not. The behaviour of the other two was not recorded.

Empty eggshell - Crawley, Sussex 19-June-2014

Newly hatched larva consuming eggshell - Crawley, Sussex 20-June-2014

First Instar

The freshly emerged larva is approximately 2.5mm long, with a black head and a very pale body, but it develops a pale green colour after its first meal on the host plant. The first instar can pass in as little as 4 days, but it usually takes around 10. The following sequence shows the development of an individual larva (except where dates indicate otherwise).

Newly hatched Speckled Wood larva - Crawley, Sussex 2-June-2014

First instar larva after first meal - Crawley, Sussex 2-June-2014

Speckled Wood larva (first instar) - Crawley, Sussex 3-June-2014

Speckled Wood larva (first instar) - Crawley, Sussex 4-June-2014

Speckled Wood larva first instar (pre-moult) - Crawley, Sussex 5-June-2014

Second Instar

This stage can also pass in just 4 days, but on average it is around 6. Here it develops a green head, pale stripes on its body and the characteristic forked tail.

Speckled Wood larva (fresh second instar) - Crawley, Sussex 6-June-2014

Speckled Wood larva (second instar) - Crawley, Sussex 7-June-2014

Speckled Wood larva (second instar) - Crawley, Sussex 7-June-2014

Speckled Wood larva (second instar) showing feeding damage - Crawley, Sussex 8-June-2014

Speckled Wood larva second instar (pre-moult) - Crawley, Sussex 9-June-2014

Third Instar

This stage averages around 7 days.
After each moult of their development it was noted that the fresh larvae invariably turned round as if to eat the old larval skin, but it was always left untouched.

Fresh third instar larva (inspecting old larva skin) - Crawley, Sussex 10-June-2014

Speckled Wood larva (fresh third instar) - Crawley, Sussex 10-June-2014

Speckled Wood larva (third instar) - Crawley, Sussex 12-June-2014

Speckled Wood larva (third instar) - Crawley, Sussex 12-June-2014

Speckled Wood larva third instar (pre-moult) - Crawley, Sussex 9-July-2014

Fourth Instar

It takes approximately a further 8 days for the larva to become fully grown, at which point it achieves a length of around 25mm. As it nears maturation, the pale stripes fade from the body and it takes on an overall pale green colouration. It then suspends itself in preparation for pupation.

Speckled Wood larva (fresh fourth instar) - Crawley, Sussex 15-June-2014

Speckled Wood larva (fourth instar) - Crawley, Sussex 16-June-2014

Speckled Wood larva (fourth instar) - Crawley, Sussex 19-June-2014

Speckled Wood larva (fourth instar) - Crawley, Sussex 20-June-2014

Speckled Wood larva (fully grown) - Crawley, Sussex 23-June-2014

Speckled Wood larva (preparing to pupate) - Crawley, Sussex 20-July-2014

Part two to follow

[Neil Hulme]

Hi Vince,
Great early-stage report as always. I'm looking forward to reading the next instalment after Dickinson's Real Deal.
BWs, Neil

[Vince Massimo]

THE PUPA

In the wild the larva usually pupates on or around the food plant or on woody stems close to the ground. However, on 1st November 2009, in Caterham, Surrey, I discovered a Speckled Wood pupa suspended under a rafter in the roof of my shed, approximately 1.7m above ground. It had chosen a well-lit and well ventilated position (the roof was of clear plastic sheeting and there was an open gap at the eaves), in an outbuilding which was on the north side of the house.

Speckled Wood pupa in roof of shed - Caterham,Surrey 1-Nov-2009

I also saw a report on the Upper Thames Branch website by Martin Harvey who found a pupa approximately 1.2m above ground on the trunk of a Silver Birch tree in Bernwood Forest, Bucs on 14th February 2010.

The colour of the pupa naturally ranges from pale to dark green, but it goes through a series of subtle of colour changes in the days prior to emergence. This stage lasts between 10 and 16 days. The following sequence shows the development of an individual pupa (except where dates indicate otherwise).

Speckled Wood larva preparing to pupate - Crawley, Sussex 20-July-2014

Speckled Wood pupa (freshly emerged) - Crawley, Sussex 20-July-2014

Speckled Wood pupa - Crawley, Sussex 23-July-2014

Speckled Wood pupa (3 days before emergence) - Crawley, Sussex 26-July-2014

Speckled Wood pupa (32 hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (29 hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (24 hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (21 hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (17 Hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (15 hours before emergence) - Crawley, Sussex 28-July-2014

Speckled Wood pupa (13 hours before emergence) - Crawley, Sussex 29-July-2014

Speckled Wood pupa (9 hours before emergence) - Crawley, Sussex 29-July-2014

Speckled Wood pupa (3 hours before emergence) - Crawley, Sussex 29-July-2014

Speckled wood pupa (30 minutes before emergence) - Crawley, Sussex 29-July-2014

Speckled Wood emerging - Crawley, Sussex 29-July-2014

Speckled Wood emerging - Crawley, Sussex 29-July-2014

Speckled Wood emerging - Crawley, Sussex 4-July-2014

Speckled Wood emerging - Crawley, Sussex 4-July-2014

Speckled Wood (expanding its wings) - Crawley, Sussex 29-July-2014

All adults were released at their point of origin.

Background and other observations

4 individuals were reared from eggs rescued on 25th May and 13th June and one laid in my garden on 23rd July but only 3 survived to adulthood. One larva died of unknown causes (but essentially failed to moult at the end of the 3rd instar). In all cases, Common Couch Grass was used as the food plant.

Two larvae (L1 and L3) were reared on cut food plant and kept indoors, resulting in a fast development rate. The other, (L4) was reared in a netted cage outdoors resulting in a more natural growth rate.

SUMMARY

L1 (Female) – Reared Indoors
Egg laid on 25 May 2014 (semi-open site)
Egg hatched after 8 days on 2 June 2014
Moulted into 2nd instar after 4 days on 6 June 2014
Moulted into 3rd instar after 4 days on 10 June 2014
Moulted into 4th instar after 5 days on 15th June 2014
Fully grown and suspended for pupation after 8 days on 23rd June 2014
Pupated on 24th June 2014 (22 days after hatching from egg)
Emerged from pupa on 4 July 2014 (after 10 days)

L3 (Male) – Reared Indoors
Egg laid on 13th June 2014 (shaded site)
Egg hatched after 7 days on 20th June 2014
Moulted into 2nd instar after 8 days on 28th June 2014
Moulted into 3rd instar after 5 days on 3rd July 2014
Moulted into 4th instar after 7 days on 11th July 2014
Fully grown and suspended for pupation after 8 days on 19th July 2014
Pupated on 20th July 2014 (28 days after hatching from egg)
Emerged from pupa on 29 July 2014 (after 9 days)

L4 (Female) – Reared Outdoors
Egg laid on 23rd July 2104 (permanent deep shade)
Egg hatched after 9 days on 1st August 2014
Fully grown and suspended for pupation on 4th Sept 2014
Pupated on 6th Sept 2014 (36 days after hatching from egg)
Emerged from pupa on 21st Sept 2014 (after 15 days)

By comparison
UKB member Paul Harfield reared a larva outdoors in Hampshire in May/June.
Egg laid on 18th April 2014
Egg hatched after 16 days on 4th May 2014
Moulted into 2nd instar after 12 days on 16th May 2014
Moulted into 3rd instar after 7 days on 23rd May 2014
Moulted into 4th instar after 9 days on 1st June 2014
Fully grown and suspended for pupation after 10 days on11th June 2014
Pupated on 12th June 2014 (39 days after hatching from egg)
Emerged from pupa on 28th June 2014 (after 16 days)


Reference Images of Adults

Speckled Wood male - Kenley, Surrey 26-March-2012

Speckled Wood female - Crawley, Sussex 10-May-2006

Speckled Wood male - Crawley, Sussex 8-June-2005

Reading References:

The Butterflies of Britain and Ireland (Thomas and Lewington 2014)
UK Butterflies Website

Vince

[Pete Eeles]

Brilliant - top notch observations (and patience) once again! Well done Vince - will convert to a proper article in the next couple of days.

Cheers,

- Pete

[David M]

Brilliant - top notch observations (and patience) once again! Well done Vince - will convert to a proper article in the next couple of days.

Absolutely.

This information (to my knowledge) is not present in any book (not to this comprehensive level at least).

That's one of the many reasons why this website is so precious.

[Chris Jackson]

Excellent work Vince. Real A to Z stuff.
Chris

[Vince Massimo]

Many thanks for all the comments guys

I learned a lot from this project, because it was my first "Brown" and it also gave me the opportunity to merge all of my early observations with the new stuff. Coincidentally, another sighting of a Speckled Wood pupa, located atypically up on a tree trunk, has just been reported by Richard Fox https://twitter.com/RichardFoxBC/status ... 96/photo/1. With such large numbers of eggs being laid recently, I would expect more sightings of pupae to occur in the next few weeks.

Vince