More Doom & Gloom

  For the last twelve years I've monitored the Emperor's performance in Savernake Forest, Wiltshire, by standardised searches for larvae during the late summer / early autumn period, from the ground. The data are shown in a table on Page 236 of His Imperial Majesty, a natural history....

  This is what I look for - 

  The 2020 tally is a mere nine. This is by far the lowest total in the 12 years. The previous lowest annual total was 16, in 2019.  The mean for the previous 11 years is 55 (the running mean is now 51).  

  This meagre total is entirely due to a very poor egg lay, as the adults got blasted away by gales in late June and early July - before they'd laid many eggs. 

The quality and quantity of the sallow resource in Savernake is actually quite high at present (though sallows close to Grand Avenue remain largely unsuitable as in dry weather their foliage gets covered in dust generated by speeding vehicles - Range Rovers and SUVs mainly; see Book, pages 236-237). There haven't been any problems with sallows droughting off in Savernake (though there have been in Sussex).   

  Ben Greenaway is finding a similar paucity of larvae in Southwater Woods in West Sussex, though he hasn't finished searching yet.  

  This means that the prospects for the 2021 Purple Emperor season are, at this stage, distinctly poor. But much depends on the winter, when larval losses can be high. The last thing we need is another mild wet winter (when mortality is very high).  

  Larvae are so scarce this autumn that I've had to abandon plans to search for Purple Emperor larvae in places where the insect hasn't been recorded for ages if at all, like the Forest of Dean, some woods in Herefordshire and into Monmouthshire, and Devon. I'm only prepared to launch a major autumn larval survey campaign in terra nova after a decent egg lay.

  Ben and I hope to have large enough samples of hibernating larvae to monitor winter survival rates, so we can compare survival / mortality rates between Savernake and Sussex.  

  I'll end with an image of hope. I found two larvae on the same spray on an isolated tree in Savernake which has revealed larvae in eight of the last 12 years. It is very rare to find two close by. 

These guys deeply resent each other's presence: one will periodically invade the other's seat leaf, where they will lock horns and try to wrestle each other off. Ridiculous, but that's Emperors all over.