As well as recording and photographing butterflies and moths, I’ve also reared caterpillars. My first attempt was years ago – I tried to keep some Large White caterpillars in a wormery but after they turned out to be miniature Houdinis I was advised to put them back on the nasturtiums!

Caterpillars would not enter mein haus again until October 2009 (a month after butterflies migrated into my life in a big way) – this time I took eight ‘Brown Furry Caterpillars’ under my wing. I identified them as Ruby Tigers (my first caterpillar of this year, incidentally) and kept them at home, in a large modified plastic bottle outside, with the intention of rearing them and releasing them back in Murlough where I found them. They fed on ragwort and dandelion for a few weeks before settling down as the colder weather blew in.

That December, I brought four of them indoors for a night, and one immediately set about spinning a cocoon to pupate in. I hadn’t intended to make them do that and since the caterpillar had moulted his hair to make the cocoon I was loth to put them back outside. So I kept those four indoors, and the caterpillar went ahead and pupated inside his cocoon.

Ruby 1, or Ruby-wan-kanobe as I called her, emerged from her chrysalis on the 4th of January, and ran around with her wings every shape, before settling overnight to let them dry flat. She was less than an inch long, with red-brown forewings and vivid pink and black hindwings. It was too cold to release her so I kept her inside for her month-long life. She didn’t have a mate, so after a while she just began laying unfertilised eggs willy-nilly!

The other indoor caterpillars showed no intention of spinning cocoons for a while, and when two of them did, it turned out that they had been parasitised by ichneumon wasps, which spun their own little white cocoons on the dead caterpillars. The other indoor caterpillar died but no parasites emerged. (Sorry for being morbid!)

The outside caterpillars didn’t fare much better: the first to spin a cocoon (Ruby 5) had one parasitic fly, but Ruby 6  pupated successfully. Sadly, the last two had ichneumons.

Ruby 6 (Ricky) was the only one out of eight that survived to see Murlough again. She emerged on May 21st and I released her back where I had found her in Murlough, two days later. It’s a wonderful feeling to care for something and let it grow and release it back where it belongs!

With the project complete, I can draw a few conclusions about the Ruby Tiger moth Phragmatobia fuliginosa.

  • The species overwinters as a fully grown larva, spins a cocoon in March, pupates in April and emerges in late May.
  • Caterpillars parasitised by ichneumon wasps seem to attempt pupation later than healthy larvae, similarly to the Marsh Fritillary (ref. Jesmond Harding).
  • Caterpillars are also parasitised by a large (5-10mm) Tachinid (?) fly, which also parasitises the Drinker and Garden Tiger caterpillars (more about them in a later post).
  • Parasites kill the caterpillars after they have spun cocoons and prevent them from pupating.
  • There were high rates of parasitisation in the Ruby Tiger caterpillars in Murlough at the end of 2009.
  • The Ruby Tiger pupates for 20 days indoors, and at least 35 days outdoors.

Hopefully someone reading this might find it interesting or even important!

Species Study 2, project A: Ruby Tiger (Phragmatobia fuliginosa)

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