Friday, 11 September 2015

Day 303 - Superly Beautiful Swallowtail Butterflies

Swallowtail Butterfly (Papilio machaon ssp. machaon)
Thanks to Jane Smart for this.
Hey everyone today's Day 303 and as you know, I like to go to Norfolk on holiday. One of the specialities of around there, isn't found anywhere else in the country. I have only seen the adult form in one or two years that I have been there but I have seen the caterpillar almost every year. I wasn't lucky enough to see one this year but I did see a little Swallowtail Caterpillar on its favourite plant. The Swallowtail is, in my opinion, the most beautiful butterfly of them all.

And here the facts on these incredible insects:

  • Now, I say that they are only found in Norfolk, well they are most common around the coast there but there have been some sightings around the rest of Southern England.
  • From what I've read though the species outside of Norfolk may be a different subspecies which migrates from the rest of Europe. The picture I have here of the adult is that species which is Papilio machaon ssp. machaon. 
  • The ones in Norfolk are Papilio machaon ssp. britannicus and are indigenous to the UK but is our largest and rarest butterfly.
  • There are only a few differences between them, the British species is meant to be a bit smaller and darker with wider black markings.
  • Now, according to everywhere I have looked and all of the information that I have been told, the caterpillars will only eat Milk Parsley, but is that really the case?...
Swallowtail caterpillar also beautiful!
  • When I go to Norfolk, I always go on a boat trip on the Norfolk broads by someone called Ross. He's very friendly, very good with engaging people, a great sailor and incredible with nature. He was someone who told me that they only eat Milk Parsley but last year I was on a boat trip with him and we discovered something that he had never seen before. A Swallowtail Caterpillar feeding on Hemp Agrimony! His suspicions were that he would never make it and we would fall ill and die because they have evolved to eat Milk Parsley and that's all they have been recorded eating on. The next year though, we asked him what had happened, and he said that it had spun a cocoon and turned into a butterfly.
  • Now, I also said in the pre-amble that I am usually a bit late to see them, that's because I usually go down in the Summer holidays, about the end of July time, but the problem is they are only usually seen from May to mid-July.
  • There is sometimes a second brood but I miss that as well as it tends to be in mid August
  • They are the largest UK butterfly, about 76 mm -83mm  for males and 86mm - 93mm for females! That's quite a big wingspan! The caterpillars are quite large too, about 4cm long.
  • The breed only on Fens and Marshes, the same sort of places as Irish lady's Tresses, Petalwort and the Yellow Mantella Poison Dart Frog.
  • The adults feed on flowers at dawn and dusk, usually attracted to Ragged Robin and Thistles.
  • There is usually just one breed of them in a year but in some years, there can be a small second breed.
Two stages of caterpillar.
  • Their eggs are lain singly (this will be so if one plant gets wiped out, there are loads more that are OK) on their food plant, Milk Parsley in a perfect sphere. They hatch in a week.
  • Like yesterdays Shield Bugs they have a number of instars, or stages of growth, the fourth instar is the big bright caterpillars in my photos.
  • Something they have to help them not get eaten apart from their bright colouring is a funny bright orange organ called called an "osmeterium". When the caterpillar is threatened they stick it out and give off a pungent smell of rotting pineapple!
  • I said further up they are our rarest butterfly, so I'm glad to have seen them if not been able to photograph one (as they fly really fast!). I read somewhere that they are now at only 1% of their earlier population levels but I don't know when that was. They are very dependant on the habitat they need being well managed and all of the Norfolk Broads has been made protected area to help them.
Here are a few links to some more information

Hope you enjoyed,


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