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Thursday, 5 June 2014

Raising Swallowtails - Part 7

Back to raising Papilio machaon Swallowtail caterpillars again for the 3rd year. This time though, instead of bringing in caterpillars that I've found outside, I have been able to start right from the very beginning as I was lucky enough to discover a load of eggs on my Bronze Fennel. So in a way this is Part 1!

Swallowtail egg when I brought it inside on 7th May;
not long after this they turned a brown colour.

To keep the fennel as fresh as possible I put it in a jug.
There were 5 eggs on these fronds.

After a long wait wondering whether anything was going to happen, whilst the fennel turned yellow and I feared the worst, suddenly all the eggs turned black! And then they started hatching, although I missed that bit, not that I really was going to sit and stare at eggs through a magnifying glass for hours on end!

Egg just before hatching showing some markings through the shell.

Once they started hatching I had to get them onto fresh fennel which wasn't easy. One refused to budge for about 24 hours so didn't get anything fresh to eat, and I may have harmed it trying to get it onto the fresh fennel (later a friend recommend using a paintbrush which made it a lot easier). So that one didn't survive but the other four did. During this time of rearing them I found another egg which I brought in, and inadvertently brought two more tiny ones in on fennel which I'd picked to feed my babies! So I have a total of seven now, at varying stages of development.

As this is not a scientific study and I cannot say which stage is a specific instar (as how on earth you can tell when something 2-3mm long has moulted), I am calling them 'stages' for the purposes of this post. There were times when two would be at different stages despite being the same age, and one time when one which was much smaller had a moult and missed a stage and suddenly became just like some much bigger ones which moulted at the same time! 

Note: I have just discovered after much searching that the UK form of this butterfly has 5 larval instars. It may be that in my photos below, stage 3 is just an older instar 2 as the UK Butterflies site says that they develop more pronounced colouration at instar 3. However the British one is a subspecies Papilio machaon ssp. britannicus and my continental ones Papilio machaon ssp. machaon are a different subspecies, although I doubt there is any difference in the larval development.  

Stage 1.
One of the first to be born on 15th May.

When freshly emerged the caterpillars measured about 2mm and were jet black with just the faintest hint of a white marking on their backs. This soon became apparent as they grew. I know there are other caterpillars which have these white markings and they are supposed to make them resemble bird droppings, foiling predators at this early stage before they get their bright red markings, which is another defence mechanism, indicating that they may be poisonous.

Stage 2.

Stage 3 (or possibly an older Stage 2!!).

This one on the side of the glass bowl that it is living in is the same age as the one above,
but I have to assume this is Stage 4 as it is quite different
(and now think this is Instar 3, talk about confusing!).

Stage 4 again.

It's been very confusing taking photos and trying to keep records because I've got caterpillars of all sizes now! I did actually get to witness the last half of a moult which is something I have missed in previous years, but that will be on my next post. After moulting some of them eat their moulted skin, which I imagine contains nutrients, but I have no idea why some do and some don't.

I discovered this one just after it had moulted and turned into Stage 5,
because it was eating its moulted skin.

Same Stage 5 one again just about finished eating its skin.
It didn't want all of it and just dropped the rest.

One thing that alerted me to the fact that a moult had happened when the caterpillars were small were the head capsules in the bottom of the bowl. Because they were larger than the frass (poo) I was able to spot them!

Head capsule from a tiny caterpillar.
It only measures about 1mm.

Stage 5 a day or two later and looking pretty smart now with lots of red for danger markings.

The head is getting the familiar Swallowtail black and white markings.

Stage 5 again.
So much easier to photograph when they get bigger!

They are only about 1cm long at this point but they have a huge growth spurt towards the end - I have three currently up to Stage 7 which I think might be the final instar before pupating, but only time will tell! I will continue on another post because I've got plenty more photos.  


  1. Great photos and descriptions, Mandy! They are pretty when they get to the later stage to me because I am not deterred by the reddish colour! ;)
    The Dainty Swallowtails (Papilio anactus) that I raised have a defensive fork-shaped organ called the osmeterium which pops up and emits a pungent odor to deter being eaten as well as being orange and black.

    1. Thanks Kim. They do have those osmeteriums, which I've seen quite often, but can I get one to pop them out for a photo? Absolutely no way, even when I was mean and squeezed one of them! I've never smelled a bad smell from them though - maybe that's something that humans can't smell?

  2. Jealous.....

    Love the aposematic colours, it'll be very interesting to watch them through the rest of their 'turning into flutters' process. We had Swallowtails on our local reserve a few weeks back- possibly released because they're only in Norfolk here now.

    1. Heehee! I'm sure you've already posted something else I want to see by now..... :-) I do keep watching them all the time as they are really fascinating especially now I have much bigger ones. Just watched another one eating a moult this morning.
      Must have been great seeing the ones at your reserve, I hadn't realised until I moved over this side of the channel that they were only in Norfolk. There they are much fussier about what they eat, here I grow dill for them and they also eat carrot greens.

  3. Great post Mandy and fascinating to read, would be hard to stop watching them all the time... look forward to the next stage.
    Amanda x
    ps if you get chance take a look at JJ's Blog I think you will like his photos of insects.

    1. Thanks Amanda and I do keep watching them! Just took some more pics this morning.... :-) I'd better get a move on organising the rest of the photos.
      Thanks for telling me about JJ's Blog cos the photography is superb and the bugs really interesting.
      Saw an Alder Fly yesterday (first time ever) but didn't have camera with me, grrrrrr! It was in the veg patch on a spud leaf!