Tuesday, 15 September 2020

Magic or Miracle

This is getting ridiculous. There I was this morning, with Mrs N, having coffee in the garden – their garden – with a couple of local friends when I noticed a small-to-middling pale brownish butterfly fluttering about near the top of a tall shrub, then settling right in my eye line, but too far away to be identified. I got up and walked over to take a closer look, and... But you're probably ahead of me already – yes indeed, it was another Brown Hairstreak! That's two, of the four I've seen in my whole adult life, both spotted in the past few weeks (see 'And Then...') and both coming as a total surprise, the last thing I expected to see. This was another female, quite faded – and no wonder, this late in the season – and less lively. She spent a while investigating the leaves she was on, then flew away rather sedately. Two Brown Hairstreaks, both quite out of the blue – what a summer this has been...
   I have been reading (in Jeremy Thomas and Richard Lewington's beautiful and authoritative Butterflies of Britain and Ireland) about the life cycle of the Brown Hairstreak, which is – as with so many butterflies – quite a story. When the caterpillars, which look like tiny green slugs, come down from the trees to pupate, the chrysalids that they become are looked after by ants, which respond to a chirruping call made by the chrysalis (how?). Some Blue butterflies, which have all kinds of complicated relationships with ants, also produce chirruping chrysalids. Despite their attendant ants (Myrmidons, you might call them), the Brown Hairstreak chrysalids are vulnerable to predators, including mice and shrews. Thomas vividly describes this predation:
 'Once [a chrysalis] is unearthed, a shrew pounces on it in a frenzy of excitement and squealing, tearing and scattering the case into tiny fragments, while gobbling up the sticky contents. A mouse is more restrained. It sits up on its hindquarters holding the chrysalis in both hands, as a squirrel might a nut. It neatly nibbles the chrysalis until not even the hard cuticle remains.' 
  The 'sticky contents' are the undifferentiated goo into which the caterpillar dissolves before re-forming, as if by magic or miracle, into a butterfly. Astonishingly, experiments have shown that adult moths (which go through exactly the same metamorphosis) can retain memory of what they 'learnt' as caterpillars. e.g. avoidance of a particular odour – this after a near-total dissolution of the tissues and the nervous system. How can that be? 


  1. Wow. What else can one possibly say?

  2. Nor was that the last of the Brown Hairstreaks – today (22nd Sept.) I saw another one, down at the local nature reserve. Another female, appropriately enough in the Butterfly Garden. Settled briefly, but long enough for a definite ID. What a year!