In Savernake Forest yesterday, April 28th, I saw nine larvae: three were in the 4th instar (L4), with one nearly half-way through that stage; the other six were busy skin changing to L4.
Savernake is a 'late' site. Larvae will be far more advanced in Sussex and Surrey (probably all in L4, with perhaps some approaching the L4-L5 skin change).
An early flight season remains on the cards, though much depends on May's weather. Larvae can shoot through L4, but if the jet stream jumps south (and some computer forecast models suggest a very cold spell here next weekend) then larval development will slow right down.
It's too early to call, so watch this space. Last year my prediction for the start of the flight season at Knepp, made in late May, was 24 hours out...
What I can say is that larvae have come through the winter and early spring periods in good numbers. Winter predation was Low-Moderate and early spring losses were officially Low. That's good. This year could see another strong emergence,
Here's one of yesterday's early-L4 larvae -
And here's a larva changing from L3 to L4 -
Last week, in Heddon Valley on the N Devon coast, we found a fully-grown Dark-green Fritillary larva, and High Brown larvae in L5 (out of 6 instars). At that rate, DGF is likely to appear there around May 20th and HBF around May 27th. And yesterday, I had a half-grown Silver-washed Fritillary larva crawling up my trouser leg... Here's adippe -
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