The Orange-tip Butterfly

For many years, we have had self-seeded Garlic Mustard plants in our garden and for many years I used to weed them out, but never sufficientlyenough to stop their return. However, a couple of years ago, I read that Garlic Mustard is a favoured plant for the caterpillars of Orange-tip butterflies, as well as other crucifers, including Cuckooflower.

In 2021 I decided that I'd let a couple of small patches of Garlic Mustard grow. Sure enough, as the plants flowered, they started to attract a few Orange-tips. This first one, however, was on white Bluebell.

Orange-tip (Anthocharis cardamines) (male) - garden on 12th May, 2021

Orange-tip (Anthocharis cardamines) (female) - garden on 16th May, 2021

The female initially detects a suitable plant for ovipositing by sight, and once landed confirms the suitability through chemically sentive cells on the feet. Sadly, it seems that I omitted to take any photos of the tiny eggs that are deposited.

The eggs hatch in a week or two and intially the small larvae disappear into the flower. They then start to feed on the developing seed pods. It is said that, if food is in short supply, cannibalism can occur - something that I didn't realise until earlier this year. Some photos of caterpillars in varying stages of growth are shown below, the last one showing the typical eating style of this species.

Orange-tip (Anthocharis cardamines) (larvae) - garden on 9th June, 2021

Orange-tip (Anthocharis cardamines) (larva) - garden on 13th June, 2021

I was keeping a close eye on developments, although I failed to record how many larvae if found, but memory suggests it was around ten specimens. They then started disappearing and I was sure that they'd not reached sufficient maturity to pupate. It soon became apparent that they were being predated by Blue Tits. When it got to the stage that only two were left, I decided to take matters in hand and remove them from the garden.

I'd bought a folding rearing cage earlier in order to raise Vapourer Moths, and this seemed ideal, so I quickly acquired a couple more and put the two larvae on a cutting of food plant in one of the cages. All went well for a while and then one disappeared - and we now know why, don't we!

Eventually, the remaining one pupated. I have since discovered that usually the larvae leave the food plant in order to pupate, but I hadn't given this one the choice! It did however, find an acceptable spot and formed a pupa, attached to the stem by a silken thread. There pupae have two forms - brown and green - and this one was a beautifully marked brown one.

Orange-tip (Anthocharis cardamines) (pupa) - 1st July, 2021

Initially, I kept the pupa in the cage in my study but, as autumn approached, I realised that keeping it in a warm dry atmosphere was probably not a sensible idea, so the cage was hung up in a roofed arbour in the garden wher it had some protection but would still experience ambient temperatures and humidity

There were no visible problems with the pupa over winter and, as spring drew nearer I started keeping a closer eye on things. By the beginning of April, I was starting to get a little worried as the pupa seemed to be getting darker and shrinking. I was checking it almost daily and had checked it in the morning of 14th April and still nothing seemed to be happening. However, Lindsay and I were sitting having a coffee in the conservatory in the early afternoon when Lindsay exclaimed "the Orange-tip's out!"

Not knowing how long it had been emerged for, I was keen to release it as soon as possible, so only grabbed a record shot through the cage before opening the cage up to give it its freedom. We'd reared a beautiful female!

Orange-tip (Anthocharis cardamines) (female) - garden on 14th April, 2022

A couple of days later it occurred to me that maybe I should take a shot of the empty pupal case. I'm pleased I did as it shows that the beautiful markings are part of the case, and the silken thread is still holding strong. You can also see how the back of the case has peeled backwards to allow the emergence. The other thing that you can see in this shot is how the seeds are lined up in those pods.

Orange-tip (Anthocharis cardamines) (pupal case) - garden on 16th April, 2022

We have rather a lot of Garlic Mustard this year, which is not necessarily a good thing as I have read that females favour isolated large plants on which they lay a single egg, thus maximising the food source and minimising cannibalism! Maybe I should thin out the patches ?

I'm not sure what my next blog post will feature, but it might be an account of my garden mini-pond which has yielded a surprise or two this year.

In the meantime, please take good care of yourselves and Nature. Best wishes - - - Richard