Urban Purple Hairstreaks

I had a most unexpected and delightful walk to work this morning. As I was about to cross Westbourne Avenue, where a water leak has been repair, a passer-by flushed a small butterfly from the barriers. I thought it was probably a Holly Blue, but when it settled with wings closed on a privet hedge nearby, I realised it was a hairstreak! I fumbled for my camera as it fluttered along the hedge into a front garden, where it sat with wings open. With shaking hands, I was able to take a photo (below), confirming the id as Purple Hairstreak! 

The first Purple Hairstreak

The Avenues is a very leafy part of Hull, with large gardens often holding large trees. In fact, there is a mature, spectacular oak at the back of the Adult Education Centre on Park Avenue not far away, and, as I walked past, I wondered if the wind might have blown the small butterfly away. I carried onto Jack Kaye fields. A Speckled Wood by the entrance to the fields, by an oak, reminded me to do a butterfly count, and I set an alarm on my phone to 15 min. I counted six Speckled Woods, as they squabbled around the trees. Then I moved onto the first glade. A small butterfly settled on a Whitebeam to bask in the sunshine. As I focused my camera, I got the feeling of being in a dream: it was another Purple Hairstreak! It has its wings closed and I took plenty of photos. 

Tree canopy butterflies

Purple Hairstreaks are canopy specialists, they spend much of their time on tree tops, around oaks (the larval food plant) and nearby trees, where they feed on honeydew. Although other species that obtain most of their food from honeydew, like Speckled Wood and Holly Blue, can occasionally be found feeding on flowers, or resting or fluttering low down, Purple Hairstreaks rarely come down to the lower level of trees, but they have been seen feeding on bramble or hemp-agrimony. They live up in the tree tops, and it is for this reason that they are easily missed. There are only 18 records of this species in East Yorkshire, mostly in nature reserves, but also at Snuff Mill Lane, just outside Hull, where I saw them in July and in Beverley Westwood, which has a sizeable population. They are not only found in woodland, but also along lanes and in parks with oaks. But, as these lovely, tiny butterflies, spend their adult lives up in tree canopies gorging on honeydew, they are likely to be overlooked and under-recorded. In the last few weeks I've been looking for them at Jack Kaye, staring into that small oak by the entrance, so although I was beyond pleased to find it, I was a bit astounded that it had actually happened. 

I will keep an eye on this area to check if these are isolated individuals or if there is a colony, and I plan to keep looking at oaks, wherever they are!

Oak Gall Wasps

I went for a walk the other day to the local Wildlife Garden. I was taking photos of autumn berries and when I went to see how the acorns were doing I couldn't find a single intact one. The handful of oaks in the hedge were covered in all sorts of galls on leaves, stems, buds and acorns. Some galls are quite attractive, others just plain bizarre. These galls are produced by the larvae of tiny gallwasps (Cynipidae). These wasps are one of the few a very group of organisms (with waterfleas, rotifers and aphids) that alternate in their mode or reproduction between a sexual phase (with male and females, usually in spring) and an asexual phase (females which reproduce parthenogenetically usually in the summer). Both reproductive phases often happen in the same oak species, but in some cases they occur in two different ones. The gall is a response of the tree tissues to the presence of the wasp larvae and the shape of the gall differs depending of the species of wasp. The gall offers protection and food to the growing larvae, which after pupation, emerge as adults through a hole. There are over 30 gall wasp species in britain in the common oak alone. Despite their tiny size, gallwasps have their own parasitoid species, also wasps!
 All the galls in the photos are produced by the summer, asexual generation on the pendunculate, or common oak, Quercus robur.

Marble Galls, produced by the larvae of Andricus kollari. The exit hole is visible in the middle. The sexual generation uses the Turkey Oak, Q. cerris. This wasp species was introduced in the 19th century and is now widespread.

Knopper Galls on acorns. Produced by Andricus quercuscalicis. Adults emerge in spring to produce the new sexual generation on catkins of Q. cerris (a non-native oak). They first appeared in the UK in 1960 and they are now widespread. I think the little wasp at the left of the centre of the photo is the gall wasp.

Common Spangle Galls produced by Neuroterus quercusbaccarum. The sexual generation forms Currant Galls in young leaves and catkins.

Silk Button Spangle Galls produced by Neuroterus numismalis. The sexual generation causes minute galls on leaves in spring.

Artichoke Galls produced by Andricus fecundator which lays eggs on terminal or leaf buds.