www.ukbutterflies.co.uk

For many people spring has not arrived until the first Orange-tip of the year is seen on the wing. This can vary between late March to early April in most areas except Scotland. The species is single-brooded, but there are occasional rare sightings of individuals in September. The principal larval host plants are Cuckooflower (Cardamine pratensis) and Garlic Mustard (Alliaria petiolata). Other closely related species like wild cresses and mustards are also used together with some garden species like Dames Violet (Hesperis matronalis) and Honesty (Lunaria annua).
Orange-tip ova are easy to find in April and May because of their prominent orange colouration, but when first laid they are white. Females try to avoid laying on plants which already have eggs, but in some circumstances numerous eggs will be found on the same plant.
The egg darkens as hatching approaches.
The larvae feed in the open on the seed pods of the plant and sometimes the leaves and are cannibalistic, particularly in their early lives.
After approximately 28 days the larva is fully grown and rests before spinning a silk pad for its tail and a silk girdle to support its body. At this stage, the larva can be sexed by observing whether there are two yellow spots on the back of the 8th segment. These are the developing testes of a male larva.
At this stage the second and third segments of the larva will sometimes show the embryonic wing cells developing.
After approximately 36 hours pupation begins
For a long time I have mistakenly thought that the larva started off facing the stem and then flipped round to face outwards during the course of pupation. I have only just realised that this is an illusion caused by the shape of the pupa as it enters its final form. This is apparent in the above series of images and those of the emerging female later down the page.

All Orange-tip pupae are initially green, but the majority then turn brown, so green pupae are not often found.
There are then further colour changes in the week prior to emergence.
This sequence seems to have taken longer than usual in 2012, probably due to the cool conditions existing at the time.

Some of the brown pupae are unusually dark.
The female pupae suddenly go quite pale before the adult colouration shows through the wing casings.
When they were ready they were released into the garden where I had already got some established Garlic Mustard plants.
In the first year of studying this species (2011) I saw my first Orange-tip in the wild on 28th March, which was my earliest ever sighting. The first of my pupae hatched on 8th April 2011 and the last on 19th April 2011. They were over-wintered in a cool shed on the north side of the house. This location had good natural light and ventilation, offering protection from the worst of the weather, but not warming up too readily. In May that year a mating pair was also found in the garden
In 2012 my first sighting in the wild was on 23rd March, while the first of my pupae hatched on 16th April.

Reading References:

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

Vince

Excellent report Vince.

Cheers,

- Pete

As Pete said, fantastic stuff, thanks for sharing.

Bill

Really interesting report Vince. Last year I relocated a few caterpillars from a local field that was about to be sprayed to some garlic mustard plants in a hedge row. I watched them continue to grow, but didn't find any chrysalises. This year I have some garlic mustard growing in the garden waiting for some caterpillars that may need rescuing! Hopefully I will then have more chance of finding a chrysalis.

Great report and stunning pictures Vince!

Cheers

Lee

To a novice like me, that is really fascinating. Thank you Vince.

Thanks for all the comments guys, much appreciated.

Vince

Excellent Vince, superbly illustrative and well executed images. Very impressive.

Piers.

Thanks for the comments Piers. Much appreciated .

Given the early emergance of large numbers of adults earlier in the season, we have the interesting prospect of a second generation this year. The question has already been raised by new member Hilary as to what the larvae will feed on and how they will fare.

Vince

Though the young caterpillars eat the leaves of the hedge garlic, the mature ones rest along and appear to eat the end of the seeds pods. Do they actually eat any of the unripened seed. I cannot tell from the few that I have in the garden but the top 4 or 5mm of the pod seems to have disappeared.

Hi John,

Yes, they certainly do eat the unripe seedpods and the seeds as these are the most nutritious parts of the plant. Thomas/Lewington states that the growing caterpillar soon feeds only on the seed-pod of its plant, although I have observed them reverting back to feeding on the leaves or softer stems when they run out of seedpods. This however only tends to happen if the larva is on Cuckooflower, which is a much smaller plant and is often quickly consumed.

This feeding damage to the seedpods of Garlic Mustard is very noticable, even from a distance, and endures well into the following winter when the plant stem has become woody and desiccated. This is the best indicator for finding larvae and also possibly pupae. However, larvae that feed on Cuckooflower tend to pupate away from the food plant and are therefore much harder to locate. Despite my best efforts, I have never managed to find a pupa in the wild.

Vince

Vince Massimo wrote:Despite my best efforts, I have never managed to find a pupa in the wild.

Finally.................I've managed to find one today while out on a local walk. It was on an Honesty stem.
Of all the foodplants used, it seems to me that the most number of reported pupal finds are on Honesty (Lunaria annua). Hatching could be in as little as 4 weeks time.

Vince

EDIT: This turned out to be a female which emerged on 7th May..........

I have just completed the latest update to this report. Two images have been deleted and replaced by a more detailed sequence of 8 new images showing the development of the male pupa prior to emergence. There have also been some minor changes to the text.


Vince

Fascinating and a treat to behold.

I have just completed another sequence. This initially followed a single individual larva from pupation to adult emergence, but some images were not very good, so the sequence has been updated and is now a composite of three individuals.
Having missed all of the other male emergence in 2011 and the first three in 2012, sometimes just by a matter of seconds, I was determined to capture the event in this case. For this species, apart from the obvious dramatic colour changes to the pupa, there is no sign that emergence is just about to occur. The pupa is rigid, so there is no initial wriggling to indicate that something is about to happen. All I had to guide me were the observations made on previous pupae. Judging the date was the easy part. The previous three males had all emerged between 10am and 2pm, so at 9.45am on 25th April I was all set up and waiting for something to happen. At midday, again without any warning, the top of the pupal case began to split and I finally got my sequence

Vince

Vince
What can I say - astonishing and beautiful.
You keep amazing us with the quality of your observations and photography.

Thanks

(p.s. - any photos of wing inflation?)

Just excellent, Vince!

Cheers,

- Pete

Hi Vince,

Really great work. Your dedication and commitment is to be applauded.

Good hunting.

Kind regards. Mark

I completely agree - a lovely sequence, Vince.

Thanks for posting.

Best wishes,

Lee

Beautiful work Vince! Amazing!

(Looking at your photos, I wish I have a better digital camera - like yours. )