Hartslock Nature Reserve is located on the north side of the Thames between Whitchurch and Goring-on-Thames, Oxfordshire. The site is owned by The Wildlife Trust for Berks, Bucks & Oxon (BBOWT) and managed by its staff and volunteers.
The reserve is a beautiful south facing, unimproved chalk downland hill with stunning views over the river Thames and the Goring Gap region. The grassland is surrounded by ancient hedges and mixed Yew woodland and, although it is only small (11-acres or 4.4 hectares), it is home to a very wide variety of plants and animals, some of which are extremely rare. For this reason the government has designated it and the surrounding area a ‘Site of Special Scientific Interest’ (SSSI) and the whole Goring Gap region is an ‘Area of Outstanding Natural Beauty’ (AONB).
The wildlife on Hartslock is typical of unimproved chalk downland but unfortunately, due to modern farming methods and the increasing pressures on land in the south of England, this kind of habitat is becoming increasingly rare.
 Bastard Toadflax bug Spent a lovely afternoon pottering around Hartslock today with a friend … the showers held off for for most of the time and, with all the summer flowers in full bloom, the site looked really spectacular.
One of my favourite species-complexes centers on Bastard Toadflax (Thesium humifusum), a rare perennial of short-turfed chalk downland. The plant itself is quite small but its ‘politically correct’ common name of ‘Stars in the Grass’ aptly describes the dainty little white, star-shaped flowers and the way that the creeping branches climb through short grass and herbage. This plant is exciting enough for keen botanists to travel from miles around but rarer still is the little bug (Sehirus impressus) that lives by sucking the sap of only this rare plant. They are a dark gun-metal blue colour and similar to the commoner Pied Shieldbug. Today we saw an adult and many juvenile bugs - characterised by their red & black abdomens - see the photos.
Ever rarer still though is the mildew that only grows on Bastard Toadflax - Erisiphe thesii - this has only been recorded from Hartslock and forms a downy mildew on the tips of Bastard Toadflax stems. If you see Bastard Toadflax and it has a grey mildew then you are looking at Erisiphe thesii 
No sooner have we seen the last of the Dingy skippers bite the dust then the next species are on the wing … what a crazy year it is. Today I spent a very nice time showing visitors around and while we admired the views we saw: quite a few Meadow Browns & Large Skippers; a female Chalk-hill Blue; a Small Tortoishell; and … a Dark Green Fritillary! In addition we saw quite a few tatty Common Blues and Small Heaths, a Brimstone and some other Whites (at distance).
The early emergence of mayflies has ended (Ephemera vulgata and danica) but now the real rarities are on the wing - Ephemera lineata.
Bee orchids are also just coming into flower, along with Bastard Toadflax, Yellow-wort, Clustered Bellflower and Thyme.
Found this really lovely giant aphid* today … it’s about 1cm long. There were also a few Ephemera vulgata & lineata plus all of the usual butterflies; a few demoiselles and perhaps 1 Club-tailed dragonfly.
(* Tony Irwin suggests that it might be Cinara piceae)
Had a tiring but very enjoyable day on the reserve yesterday. I was very keen to see what it looked like because we had had some heavy rain - the first for nearly 2 months! Gerry & I spent the morning workparty revisiting all the mapped squares, noting down which orchids were in flower but not looking for any of the remaining unfound plants - I think that if we haven’t found a plant by now it has probably taken a year out or withered and dried up anyway.
Much to my amazement we found a few Monkey orchids in flower (about 40) but they were nearly all restricted to the western side of the slope, where the soils were able to retain a little more moisture. All the Monkey orchids on the southern aspect were yellow and the very few that had set bud were probably going to abort anyway.
In the afternoon a pre-booked party from the Hardy Orchid Society came up to have a walk round the site. We saw just about everything that we wanted to see (including a late Grizzled Skipper) but the Club-tailed dragonflies that had been common in the morning has all buzzed off and were not showing themselves. Out of the wind there were also a few large mayflies (Ephemera vulgata) doing their courtship dance.
The recent winds haven’t abated yet so everything is blowing about up on the reserve, but in general the orchids and invertebrates are doing as well as expected. I counted about 96 hybrids in flower but most of them are small this year and a few are hiding in the grass where they are difficult to see. No sign of any flowering Monkey orchids yet either - some have buds but they have hardly grown above ground level as they wait for rain.
Club-tailed dragonflies were common today - resting on the bushes and trees around the main orchid slope and views from the top of the hill were magnificent.
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the view looking south-west
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the view looking south-east
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Club-tailed dragonfly
We have been mapping orchids since February and have been making good progress, finding most of the plants that were up last year. However this Spring has been so incredibly dry that the whole slope is parched and I am seriously worried about the chances of many flowers this year.
One of Lady orchids has already started flowering, with another in tight bud, but there is no real sign of the hybrid buds yet and the Monkey orchids are very small. Today I even found my first aborted Monkey orchid - where the leaves had completely withered away from the drought.
Here are some photos of the plants seen today:
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NOTICE The 9th October workparty has had to be cancelled due to too many clashing appointments in the team. See you on the 13th November! :)
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