Monday 18 July 2022

Holkham guided walk, 15 July 2022

A select group of four Honeyguiders met at Lady Anne’s Drive on the Holkham estate on a warm and sunny July morning. Our target for the day was creeping lady's tresses, a diminutive white orchid which is scarce but widespread in the native pine forests of Scotland but with an odd out-lying population at Holkham in the pine woodlands that were planted to stabilise the sand dunes in the 19th century. The origin of the Holkham population is uncertain - some think they might have been inadvertently introduced on trees planted in the dunes that had been grown further north. We will never know for sure.

'Gatekeeper among thousands' (Jillian Macready).
Walking out along the track running westwards behind the pines, it was obvious that it was peak emergence time for gatekeeper butterflies - they were everywhere. Also on the wing were speckled wood, green-veined whites, large and small skippers, peacock and red admiral.

 Hoverfly Eristalis pertinax (Rob Lucking).
Several great pied hoverflies Volucella pellucens hovered in front of us, occasionally landing – once on Malcolm’s hat! – and allowing to see its glossy black thorax and abdomen with a white stripe between the two. There were other hoverflies out as well but the only one we could identify from photos was Eristalis pertinax. There were also several large robberflies - possibly hornet robberfly judging by their size.

Robber fly sp (RL).
By Meals House we looked in the old cart barn for evidence of ant lions and found several of their shallow, conical pits. Helen did her best to entice some of the larvae out but to no avail. Maybe they had already flown.

Ant-lion pits among the brickwork (JM).

As we neared the end of the pine woods, we cut through towards the beach to the area of dunes where the creeping lady's tresses are found. Some forestry work had been carried out along the track and the more open areas had quite a lot of ragwort growing which in turn held caterpillars of the cinnabar moth. We also found several plants of lesser centaury. As the woodland opened out onto the dunes, we found that the creeping lady's tresses area had been roped off and within it we found at least eight spikes - some tightly closed and the others fully open.

Creeping lady's tresses (JM).

Megachile leachella, male on fleabane (JM).

Two bees photographed by Jillian, with IDs confirmed later, are of note. Silvery leafcutter bee, Megachile leachella, is the UK’s smallest leafcutter bee; the green tinge to the eyes is a feature. The BWARS website shows a coastal distribution for this species.

Heriades truncorum, female, also on fleabane (JM).

Heriades truncorum is also scarce (see BWARS website), though spreading, and is often - though not always - associated with pines, using resin to build partitions of its nest, liking dead timber with suitable-sized beetle holes, in the sun and with yellow composites, often ragwort but today fleabane.

At this point Jillian departed for Warham Camp and the rest of the group had lunch looking out over the beach. It was the section of beach frequented by naturists so we didn’t look too closely!

After lunch we walked west through the dune slacks looking for a butterfly speciality – the dark green fritillary. It didn’t take Helen long to find the first one - a rather worn specimen but it did at least sit still for long enough for us to give it good grilling and we even saw the dark green underwing for which it is named.

Holkham collage. Clockwise from top left: Six-spot burnet moth on willowherb; emperor dragonfly devouring the soft parts of a peacock butterfly which it had just caught on the wing (somehow it sucked the innards out, which were egg-yolk yellow); creeping lady's tresses, cinnabar moth caterpillars (we must have seen hundreds, they were on every ragwort plant) (Helen Crowder). 

As we wandered through the dunes, we found several more dark green fritillaries and also watched an emperor dragonfly catch a peacock butterfly in flight and take it down to the ground to eat.

The dunes themselves were very parched but we did find some common centaury and lots of haresfoot clover.

Common centaury (JM).

We retraced our steps back towards the car park. There were a lot of very fresh and brightly coloured ruddy darters sunning themselves on the track. We also found a couple of new butterflies for the day – brown argus and small copper. We stopped and lingered next to a stand of elms which have proved good in the past for white-letter hairstreak but it was getting a bit late in the day; the breeze had picked up and we drew a blank. A large, pale brown insect flew past quickly and did several circuits – not a butterfly but an oak eggar moth!

Jillian reported a successful visit to Warham Camp where she had seen chalkhill blue butterflies which added to the 15 species we recorded at Holkham gives us a very respectable 16 species overall! 

Chalkhill blues at Warham Camp (photos by JM).

Rob Lucking

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