Posted by: Ross Gardner | January 3, 2017

A winter retreat


World War Two pillbox entrance. Ross Gardner 2016

It will no doubt appear to some readers that the above image is something of an unlikely opener to post on a wildlife blog.  All will very shortly become clear.

There are a number of pillboxes dotted around the countryside of my home county of Essex, as indeed there is in other British counties.  Some 28,000 of these reinforced concrete and brick structures were constructed as part of so-called ‘stop-lines’.  These were defensive lines, often accentuating the obstacles provided by the natural lie of the land, put in place to meet the threat of a possible Nazi invasion.  A pillbox was essentially a small fortification, usually less than 3 metres or so wide (there were a number of different designs of varying sizes), from which armed soldiers could keep watch for the enemy.  The name ‘pillbox’, very likely refers to their supposed similarity in shape to the box used to carry medicinal pills.

But what of their place among the pages of this blog?  Well, besides the colonisation of the brickwork by a thriving population of wall-rue, the dark and dank interior held further surprises.  A torch shone into the gloom revealed shapes hanging from the ceiling.  They were peacock butterflies (Aglais io), 18 of them, hanging upside-down and dotted about the horizontal surfaces.  With these being butterflies that over-winter as adults, they had chosen this as their place hibernation.  With them also were herald moths (Scoliopteryx libatrix).  All but two of the 11 that I counted had either settled down in closely fitted pairs or as one of the bundle that had formed itself at the end of a piece of old cob-web that had twisting itself into kind of silken string.  Shared body-heat is evidently a more important consideration for hibernating herald than for the singly placed peacocks.

It seemed an odd place for such creatures to choose to spend the winter.  It was a cold day and felt all the more so for the thick walls repelling any of the heat of the January sun that shone outside.  I would imagine however, that conditions inside are constant, whether the sun is shining or a storm is howling.  A constant environment could be very important when trying to keep metabolism at low and steady rate for successfully seeing out the winter.


Hibernation Peacock and Herald moths. Copyright 2017 Ross Gardner


A bundle of hibernating Herald moths. Copyright 2017 Ross Gardner.

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