www.ukbutterflies.co.uk

Edit- This post was updated with additional photos of egg and early larval stages on 18th October 2012, 7th September 2013 and 12th September 2016. A full pupation sequence was added on 14th November 2013 and a further update, including an emergence sequence, was added on 12th July 2017


In the south of Britain there are generally 2 generations each year, with 3 generations in good years. Second brood adults have noticeably darker markings that those of the first brood. The Small White can be a pest to brassica crops, but not to the extent of its cousin, the Large White. This is partly due to it laying its eggs singly. The primary larval foodplants are Crucifers (like those in the brassica family) and Nasturtium (Tropaeolum majus). Charlock (Sinapis arvensis), Garlic Mustard (Alliaria petiolata), Hedge Mustard (Sisymbrium officinale), Hoary Cress (Lepidium draba) and Wild Mignonette (Reseda lutea) are also used.
Despite eggs being laid singly, females will often place several eggs on the same leaf, or a favoured location may be visited by several females resulting in a concentration of eggs.
The eggs are white when first laid, but turn pale yellow after a few days and then to eventually to orange prior to larval hatch.
Eggs hatch within a 7-10 days.
The fresh larva is pale yellow or orange upon emergence. It pauses briefly to eat part or all of the eggshell before commencing on feeding on the foodplant and then taking on a greener colouration as a result.
In the summer of 2010 I decided to grow some salad crops in pots in a sunny spot outside the back door. On the very day that the first crop of Wild Rocket (Eruca Sativa) was due to be taken, I watched as a female Small White laid approximately 10 eggs on it. I was not expecting this to happen, because I did not know that Rocket was a larval foodplant, but it is in the Brassica family, so it makes sense. The affected plants were re-potted and allowed to grow on separately. Two weeks later I finally spotted a number of larvae, but such was the effectiveness if their camouflage, that they were already 1cm long. Once I had got my eye in, I spotted some more on nearby Garlic Mustard plants. Other food plants utilised by these larvae in my garden over the following years have included Hairy Bittercress, (Cardamine hirsuta), Nasturtium, Radish, Alyssum (Alyssum montanum) and Scented Stocks (Matthiola sp).

The yellow line along the back of the larvae, which distinguishes them from the Green-veined White, does not always show up very clearly, but a careful check of an individual segment will be conclusive .
All larvae were allowed to develop naturally, until they were large enough to pupate, when I put them into separate pots with food and twigs. The vast majority of the 2010 batch and all of those reared in 2013 chose to pupate upside down on a horizontal surface, (attached by a central silken girdle and a pad of silk at the tail). All photos however are shown the opposite way round, for photogenic reasons (and because that is how they appear in books).
That was the development of the green form of pupa of which this is a better example.
The other type is the grey/brown form.
Occasionally an unusually coloured pupa will crop up.
Notes and Observations

In 2010 one of the larva found on Garlic Mustard transferred itself to Wild Rocket, which was overhanging from a nearby pot and continued to feed and develop normally. Further eggs were laid during the late summer of 2010, giving a succession of larvae and pupae. The time between pupation and emergence was 8 or 9 days and the last emergence was on 30th August. However nothing that pupated after 23rd August emerged that year, but they overwintered successfully.

In April 2014 an overwintering pupa was found to be parasitised. A fly grub emerged, pupating nearby and an adult Tachinid fly emerged on 30th April. This was identified as Epicampocera succincta by Chris Raper at the Natural History Museum.
Two more species of Tachinid fly emerged from overwintering pupae in 2019
Another common killer of larvae is the parasitic Braconid wasp Cotesia rubecula. These wasps lay multiple eggs into the bodies of young larvae and after the eggs have hatched the wasp grubs feed on the tissues of the living larva. They avoid the vital organs, keeping it alive until it is fully grown at which time they break through its skin. The caterpillar will die immediately or soon afterwards and the wasp grubs then spin yellow cocoons nearby from which the adult wasps will emerge 7 to 10 days later.
Parasitic Chalcid wasps are also a problem.
Finally a curious observation made on Sea-kale. The leaves sometimes have small white growths at their edges or along the course of a vein which can resemble Small White eggs.
I suspect it's purely co-incidental and not a strategy that the plant has evolved to discourage egg laying by Small Whites.

Finally, there have been occasional records of Small White larvae overwintering in sheltered locations on the south coast. In 2022 I was contacted by Dave Harris, who reported that a larva survived the majority of the winter of 2021/2022 on Nasturtium in his garden in Newhaven, Sussex. It pupated on 4th February 2022 and the butterfly emerged successfully on 21st May 2022.

Reading References:

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


Vince

Hi Vince,
Good stuff! Some very nice piccies there.
Neil

Seconded - wonderful commitment and observations!

Cheers,

- Pete

Ditto, great images and observation!

Thank you all for your kind comments. I aim to complete the series of photos in the Spring by documenting the final development of the larva that pupated on the twig.

I have also been working on a series of Orange Tip photos (larva and pupa), which will also be completed in the Spring. I am particularly interested to see how these develop, as I have never observed a pupa of this species in the hours before hatching.

Vince.

I have also been working on a series of Orange Tip photos (larva and pupa), which will also be completed in the Spring. I am particularly interested to see how these develop, as I have never observed a pupa of this species in the hours before hatching.

I am doing the same, never saw one hatch either but would like to and I am going to set up a time lapse near to when it hatches to capture the moment using a remote to get it (my last pupae died and don't want this to happen either). Be good to see your images when time comes, probably be better than mine.

Here is a final update on this item. I have been waiting for over 8 months for a particular pupa to mature and hatch in order to complete a full sequence of images for one individual.
The resulting female had already dried her wings and was ready to fly by the time I realised she had emerged, so she was released without any photos being taken.

Vince

Some more very nice images, well captured.

Thanks for the comment Dave. This year has been very different, with no larvae in the garden at all (except the ever-reliable Orange Tip), despite growing a varied number of foodplants. Not even a sniff of a Large White on my Nasturtiums

Vince

Oh Vince...I could cry for you, mate!

It's still a stunning piece of work though, and you did very well with the Orange-tip sequence. Well, lets face it, they were simply brilliant.

So...better luck next time???

Cheers.

Gibster.

Shed no tears for me, Mr. G, it's the butterflies we should be concerned about. I'm sure they will bounce back, and as long as there are people out there who care about these things, all should be well

Cheers,
Vince

The original post from September 2010 has now been updated with additional photos of eggs and early larval stages, together with a full pupation sequence. Representative images of adults are now gradually being included into all of my early-stages reports in order to complete the life cycle story. Other reports can be accessed here: viewforum.php?f=37
I hope to finally capture a hatching sequence for this species next Spring

Vince

The following sequence details the process of a Small White larva pupating. Note that for photographic and photogenic reasons the images show the larva in a horizontal position, whereas they usually pupate either head-up on a vertical surface...
... or suspended upside down beneath a horizontal overhang.
The following images were taken in October 2018.

Vince