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Hi all,

2017 has been a belter of a year (for me, anyways) - possibly the best since 1976! Then again, I'm talking from the perspective of someone who has taken less than a dozen photos of adults (only immature stages) this year, and I still have over 2,000 images to process!

Anyway - I've gathered up 17 Comma larvae in the last 2 weeks (from the wild) and all have pupated. As of now, all but one have been been parasitised (I'm waiting for the flies to emerge to identify them since I have their pupae). Number 17 looks ok.

I've never seen such a high percentage of parasitised host. Is anyone else noticing anything similar? Maybe this is Comma-specific.

Cheers,

- Pete

My own observations from North Kent seem to be similar in terms of parasite numbers. From Mid-June onwards, I have collected 14 comma larvae, mostly second or third instar, and had only two successfully emerge. Similarly, only one success from seven Red Admirals. And from 35 small torts (which I was hopeful about, as they were first instar) I got 8 adults. They mostly succumbed to Sturmia, with some others going down to a small black wasp. Also lost around 25% of my brimstone pupae to the little parasitic wasp, even though the larvae were sleeved from the egg stage! 2017 has been my worst year since I started rearing and releasing about seven years ago. I also lost over half of a batch of 32 peacock larvae collected in May, all to Sturmia Bella. I have seen very few Peacocks this year- and none in my garden! Last year, there were plenty. I do wonder if my practice of trying to release a dozen or so of various common species for the garden every year has actually resulted in a increase in local parasite numbers. In my defence, we had NO small torts in my locale until I released around 20 adults a few years back and they seemed to have done well since then. As a precaution I have chopped down and burnt my own (usually productive) nettle patch, but I have no idea how Sturmia overwinters.
On the flip side, it's been a cracking year for White Admirals (found my first ever larvae this year) and Silver-Washed Frits, both seen in their dozens in my local woods.

I only have circumstantial evidence myself. I've managed to find large numbers of Comma larvae at Bookham this year (more than I would normally come across) but very few second generation adults have yet to appear. Bookham is normally a good spot for Red Admirals throughout the year and they too have been strangely absent for the most part recently. Add to this I've also noticed large numbers of these Tachnid flies Tachina fera, parasitoids of lepidopteran larvae. I'm not sure how species specific they are, it seems to vary depending on what you read.

Comma numbers were abnormally high earlier in the year, Pete. I wonder whether this, in turn, has led to a highly successful year for its parasites?

I certainly found more larvae (and saw more adults) of not just commas, but STs, Red Admirals and peacocks this spring, than in previous years. It seems logical that parasite numbers would therefore also be up. And although subsequent later parasite attack seems to be bad this year, it only seems to have adversely affected Peacock adult numbers in my North Kent location: it's been a better than average year for everything else. Just this morning I counted two STs, Four RAs and two fresh-looking commas in my garden, enjoying the last Buddleia blooms (and the odd fallen apple). I guess we will need to see what makes it through the winter. Let's hope for a few prolonged frosts to wipe out the accursed Sturmia...

KeithS wrote:....Let's hope for a few prolonged frosts to wipe out the accursed Sturmia...

Hear, hear.

In fact, a good arctic blast in winter would do wonders for a variety of reasons.

hello, I just popped in to see if I could find any info about loss rates for caterpillars pupating and saw this thread.
so thought I would add my own observations on the parasitic fly issue.

all garden collected commas approx 10 survived to emerge healthy butterflies, the same with a bundle of 20 1st instar small tortoisehells
the problem we have here is with red admirals and small whites. Almost all of these garden collected caterpillars, again about 10 of each over the season survived to pupate only for a fly chrysalis to 'pop' out prior to the case hardening.

Having said that, we have had a stonking year for red admirals with counts of up to 30 on the buddlejas at any one time

Tracey

Thanks everyone for their responses - very useful!

Cheers,

- Pete

I found 12 Elephant Hawk larvae at Hutchinsons Bank, all in their last instar, and 11 were full of tachinid parasites, the last larva was only just out of its last moult so was behind the others. The other pupa i have is one found while hedgelaying disturbing its habitat. I have had Amblyjoppa proteus hatch from wild larvae in Addington, Surrey, although the wasp is not shown as occurring in Surrey, although we are only a few 100 yards from Kent. So will have to wait until next year to see if the pupae hatch into Elephants or wasps.

I must add that the Willowherb patch they were on is strimmed back to the ground in the Autumn and any pupae would probably be destroyed as the brush cutters cut the surface of the ground, so larvae are moved to safety in September.

In past years larvae went through to moths except 2 that had the Amblyjoppas in the pupae.