Overwintering butterfly pupae

[Matsukaze]

We found a pupa (Large White I think - I'll post a photo in due course) whilst doing some work on outbuildings this weekend. As we had disturbed it from its surroundings and cannot really put it back I would like to overwinter it safely and release it next spring. How is it best to look after it? I haven't done this before.

[Vince Massimo]

The pupae of the Whites are very easy to overwinter. If it is not possible to put the pupa back in the same place as you found it, then the next best option would be to find a cool and draughty outbuilding. Place the pupa in a shallow tray and put it in a spot which gets daylight, but is out of any direct sunlight. As spring approaches it is important that the building does not warm up too readily, so you may have to move the pupa to to a more sheltered spot in order to avoid early hatching. Assuming the pupa is viable and disease-free, the only problem you are likely to encounter is predation by mice (or the occasional giant spider), so you will need to protect the pupa with a fine mesh wire cage.

It is also possible to overwinter pupae by putting them in the fridge (at 4-6 degrees centigrade) in an airtight plastic tub. They don't need to go in until February and can be removed during the month that they are due to hatch. I have not personally tried this option because I have a convenient outbuilding and, in any event, would encourage overwintering conditions to be kept as natural as possible.

Trying to overwinter a pupa in the house would be unlikely to succeed because the conditions would be too dry and warm. This could lead to either death by dessication or early hatching.

If you are able to post an image of the pupa, it may enable me to provide some further detailed advice.

Vince

[Matsukaze]

Hi Vince,

Thanks for the advice - I'll see what I can sort out.

[Vince Massimo]

We found a pupa (Large White I think - I'll post a photo in due course)

Looks like a Large White to me as well.

Vince

[Matsukaze]

Excellent. I will have to delay planting the cabbages until after it is on the wing.