I met up with Simon Primrose at 0930 on Saturday at the Church at Grafton Flyford for another Brown Hairstreak search. The weather was just about ideal: blue sky with only a few fluffy white clouds, and not much breeze. As we walked down though the fields towards the wood we checked one potential Ash on the way. There was something there, either a very tatty male BH or a Purple Hairstreak. It was so frayed that it was impossible to tell for certain, so we decided to move on. We went and checked another potential Master Tree on the southeast edge of the wood. Although there was a fresh Red Admiral, Comma, and Speckled wood taking it in turns to bask on its leaves we didn't see any BH. Reasoning that if there were any BH males there then they would have seen off the interlopers we moved on again, heading towards the Orchard area.
Along the track at the side of the area cleared of conifers we encountered a very fresh selection of butterflies. On Devil's-bit Scabious was a near perfect Brown Argus. We also saw Meadow Brown, Red Admiral, Comma, and Silver Y. Later on we would see Small Copper and a selection of whites, so it is still well worth a visit to Grafton for all the other late lepidoptera.
At the Orchard we bumped into fellow enthusiast Ian and started a search for egg laying BH females. It was quiet until 1145 when it all kicked off. In a short window between 1145 and 1315 I identified 4 separate females. Simon saw another 2 independently. I think Ian said that he had seen 2 more in the wood, but I can't remember for sure. Lloyd joined us and confirmed that he had seen one further down the meadow area and 2 more in the next field. So that's at least 9 definite separate individuals plus whatever Ian saw. At 1315 it stopped as suddenly as it had begun with no further sightings.
During the hour and a half we watched as females would bask on a Blackthorn leaf then head down a young stem. As they descended they would appear to feel with the tip of their abdomen for a suitable spot to lay an egg. This would usually result in an egg being laid in the heal of an offshoot. In this way we were able to count 7 eggs. On one twig there were 3 eggs in very close proximity to each other, plus another near by. The lowest we found was only about 6 inches off the ground, with the others at about 18 inches.
I'm looking at the egg emergence time of around April, and being about 6 months away from the August September laying period it will have similar sunlight patterns. I wonder if the reason that the BH only seems to use the peak of the day now is to ensure that in 6 months time the emerging caterpillars are on the optimum spot for most exposure to sunlight and therefore most advanced Blackthorn leaf growth. Just a theory; what do others think?
Correction: ***In answer to my point above, just realised that it's not the 6 month gap that determines the similar day length. Rather, it would be that eggs are laid and hatch out a similar time period after and before the June 21st longest day.***
I managed to photograph each separate sighting of a BH and knew that I had seen at least 3 individuals at the time. When I sifted through photos at home I was able to identify a fourth. Here are the photos and time taken. It is worth comparing the condition of these taken on the 15th with the photos that Neil Freeman took the previous Saturday the 8th.
Individual 3 taken at 1239.
(Notice that within the space of 2 minutes further damage to the top left wing has occurred).