Tortoiseshells in April...

Small Tortoiseshell, Lower Bush, April 1st.

Small tortoiseshell larvae and old larval tent, 23rd April 2017

These once-common butterflies are sadly in decline, largely thanks to a parasitic fly Sturmia Bella. These disgusting brutes have found their way over to the UK from continental Europe and have survived due to our milder winters these days. They lay their microscopic eggs on the nettle leaves where the caterpillars are feeding.  The caterpillars ingest the eggs, which hatch out inside the caterpillar. The fly larvae eats away the caterpillar's insides, but not so much as to kill it before it pupates.  Once the host caterpillar pupates, the fly larvae eats its way out of the host and slithers off to pupate itself.

Caterpillar losses can be 100% from a colony such as above, although fortunately this lot seemed to escape parasite attack and seemed to produce a fair number of adult butterflies given be the numbers I saw in May.  I took a dozen or so of this colony and raised them all to adults, releasing the butterflies just to try and make sure there will be a few around to keep the local population going.

All of the nettle-using butterflies (Small tortoiseshell, Peacock, Red Admiral and Comma) suffer from Sturmia attack, but the tortoiseshell and peacock are hit worst because the caterpillars live in colonies, making it easier for the fly to pick them out.

Going bats...

 

Noctule bats over Upper Bush...

I was pleased to be invited by an old former colleague of mine to go bat watching in and around the woods to the west of Bush Valley in Cuxton. Red Wood is part of the Halling and Trottiscliffe Escarpment SpecialSite of Scientific Interest, an area which covers most of the local Cuxton woodland from Upper Bush, up either side of the valley and over the hill through to Pilgrims Road in Halling.

The north end of Red Wood is an old chestnut coppice, but Jeff told me there are some big old chestnut trees in there where the bats like to roost during the day. This was news to me as I thought bats hid out in churches, barns, crypts and people’s lofts, but apparently not.

In the early evening, Jeff took me to show where he had found a colony of Noctule bats roosting.  How he how found it I don’t know, but we picked our way through the coppices until we came to a couple of great old chestnuts, just coming into leaf but cracked and worn and in pretty poor shape. These were just the things for these bats, however, and indeed you could see the guano all around and all over the branches of the trees. 

It was a bit too dark in the woods to take any decent pics and as the bats were already active I didn’t want to use a flash. I thought bats had an ultrasonic squeak but you could hear these chattering away as they left the trees and shot out towards Upper Bush. There were probably 40-50 bats emerging from the hollow trees as we watched. Jeff told me they were Britain’s biggest bat but they look a little bit like slightly over-sized, rather chubby House Martins, with a powerful, flappy flight.

Jeff had a gadget that allowed him to hear the ultrasonic squeaks as well which is how he knew for definite that these were noctules, although their appearance is fairly distinctive. 

I tried to get a video but the light seemed too poor for my camera (which was annoying as it still seemed quite light to me) so we made our way eastwards out of the woods and past Upper Bush farm and up by Longbottom Wood. You could see at least a dozen or so Noctules climbing up and then swooping back down over and across the valley to grab whatever munchies they could. We spent about half an hour or so watching them fly over Bush valley until it got too dark to see anything.

Despite not being able to photograph one clearly, it was an enjoyable experience. Jeff said that this was the largest colony of Noctules he knew of, although they tend to disperse in the spring and summer to breed.

By now it was around 8.30 and as the moonless sky began to darken, we headed off to the White Hart, well pleased with ourselves.