Thursday, 12 May 2016

The butterflies of Castle Hill Local Nature Reserve, Newhaven

Transect walk 2016 season, week six

Thrift in bloom

After a slow start to the year, this week's transect walk saw a positive increase in activity around the nature reserve with 18 species and 102 individuals seen. A growing number of day-flying moths are active now and take off as you walk along the clifftop and undercliff paths. This includes the migratory moth the Silver Y, which has begun to arrive from continental Europe, aided by the south-easterly winds in recent days. Burnet Companion is always a welcome sight in the herb-rich areas of grassland. Plenty of White butterflies and a Brimstone were also seen above and below the cliffs, especially around the dense patches of Hoary Cress which hug the base of the cliffs, to which the Small White is attracted.

Male Speckled Wood butterflies have now established their territories along the shady paths to the north of the reserve; they swoop up and challenge many who invade their patch of dappled sunlight. A Brown Argus seen near the Lookout is the first reported sighting in Sussex this year and is the earliest it has been recorded at the reserve.

Patches of gorse are alive with the small Grey Gorse Piercer moth, which flies up in tiny swarms when a branch is knocked. Green Hairstreak butterflies, which to the untrained eye are difficult to see in flight, are also active around the gorse and are apparently increasing in number each year. This year has been the best since we started the transect walk six years ago.

During my walk I set out a pheromone lure and attempted to attract male Emperor Moths - a species which has not previously been recorded at Castle Hill LNR. The lure emulates the pheromone which is broadcast by freshly emergent females. I had not used one prior to this year and some were bought by the Friends of Castle Hill to confirm whether this common, yet elusive, stunningly beautiful moth is present. It is! I recorded two males in the area near the pond. This brings the moth and butterfly species list up to 332.

Emperor Moth male

Other insects seen during the walk included a mating pair of the tortoise beetle Cassida nobilis, probably the first time this species has been seen at the reserve. A pair of Stonechats was seen feeding a fledgling juvenile and more were heard deep in the bramble, no doubt preparing to fly the nest. It reminds me that the season is moving on apace.

Grey Gorse Piercer
Here's the full list (18 species, 102 individuals):

Green Long-horn (Adela reaumurella)  10
Common Nettle-tap (Anthophila fabriciana)  1
Brown-spot Flat-body (Agonopterix alstromeriana)  3
Silver Carrot Conch (Aethes williana)  2
Grey Gorse Piercer (Cydia ulicetana)  30
Straw Pearl (Pyrausta despicata)  2
Emperor Moth (Saturnia pavonia) 2 males - new species
Brown-tail (Euproctis chrysorrhoea)  1 larval web
Silver Y (Autographa gamma)  2
Burnet Companion (Euclidia glyphica)  1
Brimstone (Gonepteryx rhamni)  1
Large White (Pieris brassicae)  4
Small White (Pieris rapae)  23
Speckled Wood (Pararge aegeria)  6
Peacock (Aglais io)  5
Small Tortoiseshell (Aglais urticae)  3
Green Hairstreak (Callophrys rubi)  6
Brown Argus (Aricia agestis)  1 - first known Sussex sighting in 2016

The striking hoverfly Helophilus pendulus

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