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Prees Heath Report April & May 2019

Regular visitors to the reserve may have noticed in recent weeks that some of the oak trees have been almost leafless. This is not the result of the trees coming into leaf a bit late or some disease, but rather as a result of the leaf buds and leaves being eaten by caterpillars. On one day I parked my vehicle under the oak tree on the right hand side of the access track and it was immediately evident that there were literally hundreds of caterpillars hanging down from the tree on silk threads, many of which ended up on the vehicle or on my jumper. Since then a closer examination of the tree revealed several different caterpillar species, including caterpillars of the Purple Hairstreak butterfly, which has been spreading on the reserve. However this was not the caterpillar that was dangling from the tree in their hundreds, as we think that species was the Green Oak Tortrix moth, also known as the Oak Leaf Roller moth, Tortrixviridanaa small micro-moth. 


 Purple-Hairstreak-caterpillar  Green-Oak-Tortrix-caterpillars-on--my-vehicle
 Purple Hairstreak caterpillar  Green Oak Tortrix caterpillars on my vehicle                                                                



Samples of some of the caterpillars evident on the treewere taken to Butterfly Conservation HQ in Dorset for identification by moth expert Mark ParsonsHe identified caterpillars of various moths, including Common Quaker, Small Quaker, Mottled Umber, Pale Brindled Beauty, Winter Moth and Green Oak Tortrix. It is believed that the last two species have been responsible for the defoliation. We added one more species to that list – the Dun-bar. The oak trees are already showing signs of recovering from this episode. If anyone has any thoughts as to why this has happened this year – maybe it is linked to the very warm summer last year? -pleaselet me know.


Small-Quaker Mottled-Umber
 Small Quaker  Mottled Umber
 Pale-Brindled-Beauty Winter-Moth 
 Pale Brindled Beauty  Winter Moth


  Still on the subject of caterpillars, we – 14 people in all - enjoyed a Silver-studded Blue caterpillar hunt on Wednesday 29th May. The day turned out to be cool and cloudy, however, and, despite some diligent searching, no SSB caterpillars were found. In compensation people did see caterpillars of the Purple Hairstreak – six were found on the oak tree on the side of the track. In July in recent years we have found the adults on various oak trees across the reserve. We also found the caterpillar of the Yellow-tail moth. All this goes to show that a single oak tree supports many different species, and not just butterflies and moths. We will be holding a Moth Night on Friday 27th September from 7.00pm onwards, followed by a Moth Breakfast from 8.00am the next day.



Yellow-tail moth


This spring, for the second year in succession, we have recorded Dingy Skipper butterflies on the reserve. Just two were spotted by Lucy Lewis on the northern edge of the control tower field, near the A41, in May. So it does look as though they are breeding on the reserve again – they had been recorded in the 1990s, before the reserve was purchased in 2006 - which is good news indeed. The total number of butterfly species recorded on the reserve since purchase now stands at 28.


June and July will be busy months on the reserve as people come to see the Silver-studded Blue butterflies. This year I am leading five guided walks for various community groups, as well as a guided walk open to the general public at 2.00pm on Sunday 30th June. The former RAF control tower will be open that day as well, from 10.30am till 4.00pm. 


Dragonflies and damselflies are starting to emerge on the pond. Lucy Lewis took these two photos of Broad-bodied Chasers there in May.


 Broad-bodied-Chaser,-male  Broad-bodied-Chaser,-female
 Broad-bodied Chaser - Male  Broad-bodied Chaser - Female



We held an on-site meeting with Natural England and our consultant Dr Phil Putwain in May, and this proved very useful in determining future management plans. Overall Natural England stressed that, although it is still early days for the restoration of the heathland, the results to date are encouraging. We will be continuing to use herbicide selectively to control unwanted species for the time being. 



Stephen Lewis

Butterfly Conservation Prees Heath Warden

07900 886809

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