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As I mentioned recently in my PD, I’ve taken a few Orange-tip eggs home to rear a few. The main aim was to compare those reared on Rape Brassica napus to those on the more usual LHP, Garlic Mustard. Rape seems to be the primary LHP on Walthamstow Marshes. Unfortunately, this comparison is already flawed since I’ve discovered Rape doesn’t like being cut, the flowers die off quickly without developing much in the way of seedpods so I’m unable to guarantee high quality food for them. Garlic Mustard on the other hand copes much better with sitting in water.

Anyway I’m going to do my best for them and keep them supplied with fresh food as best I can, it’s not like I’m going anywhere on holiday!

This is the one who was laid on Garlic Mustard I collected from Epping Forest on the 4th May. This first picture is from 4 days later on the 8th at 7.49pm, you can clearly see the head of the fully developed larvae ready to hatch At 10.28pm it was busy munching on his first meal. He them wandered off to rest, exhausting work this hatching buisiness! On the 9th it had found a nice tender seed pod to munch on On the 10th it looked like it was gearing up to moult to second instar (the size of the head compared to the first thoracic segment the main clue I’ve always used) The 11th it was still in its first skin and still had a healthy appetite But on the 12th it was sporting a brand new skin (note how large the head looks compared to the body) The 13th it already looked ready to moult again And tonight, the 14th, when I got home it’s already at 3rd instar This incredibly fast growth rate they have I've always put down to the high protein content of the seed pods compared to the leafy diet most other larvae have.

The next post will be the ones eating Rape over the same time period.

On the 3rd of May I collected 4 Orange-tip eggs laid on the afore mentioned Rape, Brassica napus. This is one close to hatch on the 8th May. The following morning, the 9th, before leaving for work I found the same one munching on its egg shell That evening it was eating a flower stem. On the 10th a second had hatched and was found tucking into a flower bud The one from the 9th was growing fast. The 11th. Flower buds seem to be popular amongst those feeding on Rape, although it’s a messy business. On the 12th the oldest of the Rape feeders was ready to moult. On the 13th I had managed to locate a third hatchling tucked up in the flower buds where I couldn’t get a picture. Due to the state of the foodplant they were on though I’d given up tracking them independently so I’m unsure as to which is which from now but here’s one just before moult and one just after. Today, the 14th, I collected some fresh Rape and set about transferring them onto the fresh food. Not something I’m keen on doing at such a young stage but unfortunately essential in the circumstances. The 4th egg seems to have failed so the three remaining larvae were closely inspected to make sure it was safe to move them. At my age with my failing eyes I did this via taking pictures. 2 were ok to move but the third was just getting ready to moult, indeed whilst dealing with the other two it did indeed moult, here it is mid moult. And after, wearing its old head capsule like an ill-fitting crash helmet. This is the state of the plant it was on. It caught me by surprise how fast it goes downhill, I’ll be more on the ball from now on and hopefully they’ll be much bigger next time they need transferring.

This should indeed be fascinating, Paul. Some interesting images already and I wish you luck with the denizens of both these LHPs.

Back to the one feeding on Garlic Mustard. On the 15th it was still busy growing into its 3rd instar skin. On the 16th though, that same skin was getting a bit tight and it was preparing to moult again The 17th saw it at 4th instar On the 18th it had decided to fell the top of his food supply On the 19th like clockwork, two days after its previous moult, it was preparing for the final skin change. 20th. 12 days after hatching, a handsome 5th instar caterpillar. 21st. It had moved down to eat a leaf after running out of seed pods, although this is something I’ve observed in the wild when plenty of seed pods are still available. (After taking this picture I provided it with a fresh spike of seed pods).

The three feeding on Rape are keeping up with the Garlic Mustard feeder as far as growth rate is concerned. Two are about a moult behind it and the third a further day behind which corresponds closely with the hatch dates of the three.

On the 15th they were all tucking into their new fresh food On the morning of the 16th two were ready to moult to 3rd instar, the other was tucking into breakfast. That evening the two had moulted. On the 17th the youngest was gearing up to moult. The other two happily munching, one of whom was still wearing his old head capsule on his butt, some sort of fashion statement perhaps? 18th. The oldest getting ready to become a 4th instar 19th. All three were either getting ready to or had moulted to 4th instar 20th. All three were now 4th instar 21st. the oldest about 18-24 hours from its final larval moult.

A female Orange-tip laid an egg on dame's violet Hesperis matronalis in our garden a couple of days ago - last year we had late-instar larvae on the same species, so I expect it serves as a foodplant.

All the Orange-tip early stages I've seen this year so far here in the Mendips have been eggs or first instar larvae, so yours are well ahead.

Hi Matzukaze. I wouldn’t say my ones were ahead of other population par se, even a week after your comment I was still finding OT eggs and I still have yet to find a wild OT caterpillar this year. What seems to have happened this year the flight period has been greatly extended due to the frosty April and wet May so eggs were being laid over a much longer period than usual.

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A final post to catch up with the final days before pupation. On the 22nd the one on Garlic Mustard was still feeding well and going through seed pods at a rate of knots. The ones on Rape were either side of the final moult. On the 23rd the final one on Rape was gearing up for the final moult. On the 25th the one on Garlic Mustard started to wander off, looking for somewhere to pupate and the final one to moult to 5th instar was pupating on the 29th. Despite the provision of numerous twigs and sticks all four decided to pupate on the glass sides of the vivarium I’d put them in. In order to hibernate them I’ll have to carefully use a razor blade to remove the silk from the glass and glue them to a twig at some point, I can’t foresee any issues with this as long as I’m careful. From hatch to pupation took approx 20 days. Some spent a few days wandering until pupation but the ones feeding on Rape didn’t seem to be any slower in developing and were of a comparable size as the Garlic Mustard feeder at each developmental stage. Based on my experience, Rape, Brassica napus, would seem to be a perfectly good LHP for Orange-tips.

Thanks for your observations, Paul
I never cease to be amazed that, despite appearances, the larva is still facing in the same direction after pupation.

Vince