Wednesday, 22 May 2019

Broad-bodied Chasers



I popped at the YWT local wildlife garden after work. The staff alerted me to the presence of a Broad-bodied chaser on a patch of Red Campion. I popped out to find it there straight away. It sat on the flowers and repeatedly darted to catch an insect, only to return to the same perch, flycatcher style. It didn't have to fly far as it was warm and sunny and there were plenty of small insects about. This, one of the most spectacular of our dragonflies, is my first species for the Hull Dragons challenge! A quick walk around the pond revealed there were at least 5 individuals about, each sallying from their favoured perch hunting almost in succession. All of them had yellow abdomens, including two males, indicating that they had emerged recently, most likely from the pond in the garden. They mostly ignored one another, despite being in quite close proximity, another sign that their male territorial behaviour hadn't kicked in. Despite their amazing colour, they are quite cryptic and merge into the foliage as soon as they stop.
Immature male.
This species is still uncommon in the Hull area, with only a handful of records. As I covered in a previous post, it was unknown in south east Yorkshire before 1995, although it is becoming more widespread. It is a good colonist and one of the earliest dragonflies to breed in new ponds. The pond in the garden was re-dug in February 2016, and given that the larvae only emerge after 2 or three years it is likely that the species bred in the pond the first summer after it was refilled.
The pond being re-lined in February 2016. I will post some photos of the pond as it is now in a future post. 
A walk around the pond revealed one, possibly two Azure damselflies. It is not a very large pond, but always interesting and I have records of a good range of damselflies and dragonflies: Common Emerald, Azure Damselfly, Blue-tailed, Common Darter, Ruddy Darter, Southern Hawker and Migrant Hawker. Broad-bodied Chaser is a great addition to the list!
Another immature male.
An immature female, note the wider abdomen in comparison with the males.
Immature female.

Friday, 3 May 2019

Early dragonflies and damselflies

The dragonfly season is already under way in the south of the country, although here I still haven't seen any dragonflies and damselflies. It's time to prepare though, as during May, several species emerge from their larval stages and are most likely to be encountered around ponds and wetlands. These are four species worth keeping your eyes open for as you visit suitable sites in and around Hull.
1. Large Red Damselfly, Pyrrhrosoma nymphula
The earliest flying damselfly is usually the distinctive Large Red Damselfly. It emerges from the end of April to early May, flying until late July, and peaking on the 3rd week of May. It has very uncommonly been recorded in the Hull area, even though it has been recorded in the Tickton area east of Beverley and in the eastern fringes of the Wolds near Brantingham.
2. Hairy Dragonfly, Brachytron pratense. Its early flight period (end of April to Early July) helps separate this species from related hawkers. Peaks on the 3rd week of May. This is a recent colonist to East Yorkshire and there is only one record (2018) in the Hull area, but we expect their numbers to steadily increase so it's worth keeping an eye for them. It holds breeding populations in the middle river Hull area (Tophill Low and Leven Canal).
3. Azure Damselfly, Coenagrion puella. Peaks on the 3rd week of May. It can be abundant in suitable habitats, which include small garden ponds, especially if they have abundant marginal vegetation. It's main distinguishing feature from other local blue damselflies is the spur on the side of the thorax. Several locations known in Hull. Males hang onto females while they oviposit and often many pairs oviposit together.
4. Four-spotted Chaser, Libellula quadrimaculata. Long flight period, from end of April to end of August, peaking on early June. It can be dull in flight, without distinctive features, but males are territorial and like to sit in prominent perches overlooking water, where their lovely markings can be appreciated. The dark spots in the middle of each wing are diagnostic. Females oviposit by flicking eggs into the water, while makes guard them at a distance. They are good colonists and there are records from a few Hull locations including Oak Road Lake, Pickering Park and Noddle Hill.

Tuesday, 23 April 2019

Hull Dragons: recording the damselflies and dragonflies of the city of Hull

Following on my project last year Yorkshire Dragonfly Quest 2018, with the aim of observing all the breeding species of Yorkshire dragonflies, this year I'm spearheading a collaborative, citizen science project to document the presence, distribution and evidence of breeding for dragonflies in the city of Hull and surrounding areas, which I set up with the help of Dick Shillaker, of Hull Natural History Society and Yorkshire Branch of the British Dragonfly Society.
If you live in Hull or surrounding area (i.e. from the Humber Bridge in the west to Paull Haven in the East and from the Humber boundary to the villages of Skidby, Cottingham, Wawne and Bilton) and either know or would like to find our more about dragonflies and collaborate in this challenge, you are most welcome to join the challenge.
Temporary pond at Snuff Mill Lane
Dragonflies and damselflies in Hull
I've always been impressed by the variety of wetlands and ponds (including temporary and permanent, large and small), ditches and drains found at Hull. This is mirrored on a good diversity of dragonflies and damselflies, with two sites (Oak Road Lake and Noddle Hill Local Nature Reserve) highlighted as priority sites for dragonflies in Yorkshire (over 8 breeding species, see here). Records of 17 species are available, including the recently established and still expanding Small Red-eyed Damselfly (found at East Park in 2018), Hairy Dragonfly (found at Oak Road Lake in 2018) and Vagrant Emperor at a Hessle garden in 2015 and an old record (1836), of a Vagrant Darter in the city.
Hairy Dragonfly feeding on Harlequin Ladybird, Oak Road, 2018.
Why record?
Not all these records are of breeding populations, and dragonfly species are in a state of flux due to their sensitivity to increasing temperatures, so the data collected is important to document abundance and distribution trends, also with a view of contributing to the State of Dragonflies Report of 2020.
Broad-bodied chaser at Snuff Mill Lane, 2018.
What the challenge involves
To contribute, you need to chose one or more sites which you are able to visit, in the spirit of 'adopt a site' of the British Dragonfly Society. For each chosen site (see below) you need to commit to at least two visits during the peak dragonfly season (May to September). An early visit in May-June and a late visit in July-August would be ideal minimally. During each visit, you need to make a complete list of all species observed, numbers (estimates are fine) and evidence of breeding (check out the guidelines from the British Dragonfly society). Once you have your data you will need to input it in iRecord using the available BDS dragonfly form. The data will follow the usual verification process so if you took photographs please upload them with your records.

If you would like to contribute please let me know via e-mail (a.gomez@hull.ac.uk). In particular, let me know if you have a preference for one or more particular sites so that we can make sure we cover as many sites as possible.

As part of this project, and here at BugBlog, I will cover in several blog posts what species to look for when and where and interesting aspects of the natural history and behaviour of the dragonflies and damselflies of the city of Hull.

Tuesday, 23 October 2018

Painted Ladies, the world travellers

I kneeled down and crept closer. The butterfly stood tiptoeing exposing its wings fully to the low afternoon sun, warming up. I was on the coastal path by the low cliff top at Spurn Head, a well known bird migration hotspot. This was my last Painted Lady of that year, 5th October 2014. The butterfly's faded colour and worn wings suggested that it was old and had been on the wing for a while, migrating. It still had a very long journey ahead.

Cosmopolitan and warmth loving
The Painted Lady is one of the most cosmopolitan butterflies, only absent from South America, Australia and the polar regions. It is cosmopolitan in more than one sense, as it is a constant traveller, moving in search of good caterpillar food sources and away of the cold. Unlike other butterflies, which have a cold-resistant stage - which can be the egg, the caterpillar or the adult - no life cycle stage of the Painted Lady can survive cold temperatures. In the UK, most sightings occur from May to September, with a strong peak in August.
This fresh individual from 25th July (Hornsea, East Yorkshire), feeding on buddleia, is likely to have been born locally.
A male Painted Lady hilltopping in the Swiss Alps (12th August 2015).

Through the desert and back
Painted Ladies migrate north in the spring to arrive as the summer starts in Europe, and they do the reverse flight in the autumn - just like many migratory birds - although the facts and routes of their migration have been only recently been pieced together. Unlike birds, migration is achieved in several generations - individual adults live for about four weeks - so it will be different individuals who carry out each leg of a migratory flight. Scientists used to think that the Northern European individuals overwintered around the Mediterranean and in North Africa, and that if any made it across the Sahara they might reach a dead end. Even a return journey from northern Europe was doubted, as migration is less obvious in the autumn, when the butterflies fly at high altitude to take advantage of tail winds, where they are out of sight. Research in the last few years has revealed that their migratory journey encompasses sub tropical Africa in a circuit of about 12,000 km. The migratory journey of the Painted Lady is actually the longest of any butterfly, with individuals being able to cover over 4000 km journeys, easily surpassing the Monarch! Gerard Talavera and Roger Vila, from the Institut de Biologia Evolutiva in Barcelona, travelled to four countries in the African Sahel (Senegal, Benin, Chad and Ethiopia), a band of savannah environments just south of the Sahara desert in October-November, just after the rainy season, with the vegetation is at its lushest. They visited tens of sites in each country in search of Painted Ladies. They found evidence of southbound migration, with worn individuals and directional movements, and local breeding. This is evidence that the European populations must actually cross the Sahara en masse during their migrations, to spend the winter months in tropical areas after the rainy season. Overall, they estimated that between six to ten generations are involved in the yearly cycle. 

Stable isotopes and the autumn migration
Is there an efficient return autumn migration in the Painted Lady? How can we find out? Scientists can fit migratory birds with miniature geolocators before migration, and these can be retrieved when the birds return to their breeding grounds, and the collected data allows to reconstruct their migratory routes and strategies. Unfortunately this is not feasible with small insects. There is, however, an alternative technique is at hand: to use stable isotopes. Stable isotopes, which have a lot of regional variation, leave permanent signatures of the natal origin of an insect in their bodies. The tissue development of a butterfly takes place in the caterpillar and pupal stage - often occurring in a single plant, and therefore reflects precisely the isotope composition of the particular place were the butterfly developed. If the adult emerging then migrates and is captured at its destination, or en route, the stable isotope composition of its wings provides a signature of where the butterfly developed. 
In a different study, Talavera and his multidisciplinary team collected specimens from around the Mediterranean from Morocco and Spain to Israel and Egypt just as they reappeared in early spring (February to April). They then analysed the stable hydrogen isotopes on samples of the butterfly wings. These were consistent with the presence of some locally born individuals but many others had a sub-Saharan origin, providing evidence for a return migration from the Sahel and subtropical Africa in spring.
Another likely migrant, this one a spring one, found in Flamborough head, 29th June 2015.

Next time you see one of these tattered Painted Ladies, spare a thought about the incredible distance that this small insect might have covered, and that it might have spend the last week or two flying across the Sahara, crossing the Mediterranean and moving through Europe in search of food for its next brood.

More information
The Vanessa cardui project. Here.

Talavera, G. & Vila, R. Discovery of mass migration and breeding of the painted lady butterfly Vanessa cardui in the Sub-Sahara: the Europe–Africa migration revisited. Biol. J. Linn. Soc. Lond. 120, 274–285 (2017).

Talavera, G., Bataille, C., Benyamini, D., Gascoigne-Pees, M. & Vila, R. Round-trip across the Sahara: Afrotropical Painted Lady butterflies recolonize the Mediterranean in early spring. Biol. Lett. 14, (2018).

Wednesday, 29 August 2018

Late August shieldbug gallery

While spending some time in the garden pruning trees, deadheading and generally pottering around I have come across several species of shieldbug. The top shot shows a Corizus hyoscyami, a species which is expanding north in range in the UK. I found it on the seed heads of a purple toadflax and I briefly moved it indoors for a white background photographic session.

This large and colourful bug is a Hawthorn shieldbug, Acanthosoma haemorrhoidale, which was feeding on a meadow crane's bill.
I'm not sure how I spotted this cryptic Sloe or Hairy Shieldbug, Dolycoris baccarum on a buddleia seedhead.
This forest shieldbug, Pentatoma rufipes, was crossing the path. 
Finally, a late instar nymph of a Green shieldbug, Palomena prasina, under a budleia leaf.

Click here for a great resource for the identification of British bugs (Hemiptera).