Small White Chrysalis, Parasitic Wasp

Last year I notice a number of green caterpillars on some Rocket that was growing between the slabs in our patio.

I assumed they were Small White, Pieris rapae, because I had seen adults laying eggs although I couldn't be sure they weren't the caterpillars of Green-veined Whites, Pieris napi.

Later, once I saw the caterpillars were gone, I looked all over the walls of the house for chrysalises, but could only find one Small White chrysalis.

At the beginning of April this year I was sorting out the garden furniture in anticipation of a family visit when I notice a Small White chrysalis on the arm of a garden chair.

Knowing that it wouldn't be safe I carefully removed it and placed it in a jar lined with paper towel inside one of my rearing cages.

About three weeks later I was checking the chrysalises and noticed a number of small insects climbing around on the walls of the cage. I realised that these were parasitic wasps and I found about 15 of them.

When I checked the Small White chrysalis I noticed a neat round hole in it.

I haven't been able to identify the wasps, but I am interested to know more about their life-cycle. I presume that they either lay their eggs into caterpillars or chrysalises and they must develop inside the chrysalis early in the spring. It was the 24th April when I found the wasps, a time of year when the Small White would be either still be chrysalises or would have emerged into adults. Any eggs the butterflies lay would only hatch in early June, about six weeks ahead. I wonder if there is another host that the wasp uses at that time of year.

Happily there have been a lot of Small White butterflies flying around this year, so a good number made it through without being parasitised.

Butterfly Bonanza

On Tuesday I went for a walk up to the wee valley above our house to look for butterflies. The last couple of weeks had been a little rainy and cloudy and there always seemed to be wind blowing from one direction or the other. However, on Tuesday it was beautifully sunny, 18 degrees with a slight southerly breeze.

Not far from the gate out of the woodland is a clump of Thyme, which is always popular with butterflies. When I arrived there were two Small Skippers, a Ringlet and a Northern Brown Argus on it.

Almost every Marsh Thistle flower had one or more Small Skipper on them.

If not they would likely be occupied by Ringlets.

In the short walk, of about 500 metres up the valley I counted 373 Ringlets and 199 Small Skippers. This clump of thistles had four Small Skippers, a Meadow Brown and it wasn't until I looked at the picture once I was back home that I noticed a Northern Brown Argus on the flower on the left.

There were two lovely fresh-looking Common Blues.

I counted 23 Small Heaths and 71 Meadow Browns.

There were at least 22 Dark Green Fritillaries around, although they were flying backwards and forwards, so there could have been more. I struggled to get a picture of one without another butterfly photo bombing my shot. The pictures below were all taken within 14 seconds. First a Meadow Brown tried to get in on the act.

Then a Small Skipper joined in.

And then a different Small Skipper landed just below it!

This female Dark Green Fritillary was accompanied by two Small Skippers.

This male seemed to have more extensive dark markings than normal.

I saw a total of seven Northern Brown Argus. They were all quite worn-looking, having been out a couple of weeks earlier than normal.

It was amazing seeing so many butterflies in this special valley. I have been visiting it for about 20 years and I have been watching it slowly evolve since grazing has stopped and trees have been planted. Some species, such as the Northern Brown Argus have not been so numerous in recent years, most likely because their larval food plant, Rockrose, is becoming a bit swamped by other vegetation. But other species, such as the Small Pearl-bordered Fritillary and Small Skipper have increased considerably.

Just as I was leaving I thought I should check out the clump of Thyme again and this time there were six Ringlets and a Small Skipper!