Urban bush-crickets: Roesel's Bush-cricket

I'm starting a daily series on urban bush-crickets. Checking through the blog, I realised I haven't paid much attention to these newly arrived species in the city. In 2022, I undertook a survey of urban bush-crickets, after I was made aware of the presence of several species in the city of Hull. It was an exhilarating summer: armed with a heterodyne bat detector, I explored grassy areas, marshland and brownfield sites across the city, listening for them or trying to spot them. The last two summers, I have continued with the surveys, as I have really got the bush-cricket bug! With this series, I want to write what I wish I had known when I started regarding each of the species.

Female Roesel's Bush-cricket basking, Rockford Fields, 9 October 2023. Note the curved, relatively short ovipositor and short wings.

The Roesel's Bush-cricket, Roeseliana roeselii, is a stocky species (top shot, a calling male at Sculcoates Cemetery, 28 September 2024). On first impression, if you see one scuttling through grass you think it's a small toad, as they physically disturb the vegetation with their bulk as they move. The size and colour is variable. The most common form is brown and yellow, with some green touches, but some individuals can be very green. The rim of the black side of the saddle-shaped thorax is white, yellow or green. Three yellow spots just above the base of the legs, on the thorax, are distinctive, as is a black comb-shaped stripe across the jumping legs. The species is wing-polymorphic. Nymphs growing in dense populations tend to develop long wings and are able to fly long distances. The long-winged form is responsible for long-distance dispersal and colonisation of new areas. The most common form has short wings, extending half way through the abdomen, and is unable to fly. Females are larger than males and have a short ovipositor, curved upwards. Males have modified forewings, which they use to sing (stridulate). They lay their eggs in plant stems. During mating, males provide females with a nuptial gift called 'spermatophylax' which makes a substantial proportion of males' weight. 

A male long-winged Roesel's form calling.

Behaviour. Individuals like to bask in sunshine, often quite exposed, especially in cool mornings in the autumn. Sometimes they will stretch out a jumping leg to expose the abdomen to the sun. Males start to sing while basking, choosing grass tussocks as a perch. Tussocks offer individuals protection from predators: at the slightest disturbance, they drop onto the base of the tussock and scramble into it. They are not particularly social and will compete for a good perch or sunny spot.

Roesel's are very well camouflaged in their environment and can be tricky to spot. Try to find a calling male Roesel's male from a perch on tall grass. (tip: the Roesel's is at the bottom third of the centre of the image. There is also a Long-winged Conehead on the centre top third.

A typical urban unmown field holding Roesel's.

Habitat. Thought to be associated to salt-marshes and dunes, the species has been shown to be little limited by habitat and can now be found along road and path verges, grassy fields, brownfield sites, and any habitat that includes rank grasses. 

A Nymph Roesel's busch cricket. 28th May 2023, my first observation of the year for the species.

Field craft. How do you find Roesel's bush-crickets? The first nymphs appear in mid to late May. Nymphs can be found by sweeping grass with a net. Adults appear at the end of July, and are best searched for. Male's stridulation is within the human audible range, but it is a high-pitcher whirr, that is easier to hear for children. Many middle age people are unable to hear them at all, so using a bat detector set to 20 KHz makes it easier to detect them. The call is a continuous whirr that has been compared to an electric buzz. Once you are close enough so that the sound is quite loud, you can try and pinpoint where the calling male is perched by swaying the bat detector left and right and up and down. I find binoculars very useful, to scan suitable perches from a couple of meters with minimal disturbance to spot individuals. With a bit of luck, once located, using slow movements, they can be approached to close range. Males tend to call during the day in sunny weather, unless they are already warm, then they will carry on calling. Searching at suitable sunny spots for basking individuals can also be rewarding, especially on bramble leaves next to grass, where they can be more obvious. Roesel's season winds down as October progresses and the last adults die off with the first frosts, their eggs surviving in grass stems over the winter. 

A long-winged female Roesel's. I saw it flying and landing on the short grass of a playing field (31st July 2020), this is the only photo I took, as it immediately flew north. 

Range expansion. Roesel's have undergone a spectacular range expansion in the last decades, from the south east corner of the UK. The first record in Hull was in summer 2015. They are now widespread in East Yorkshire and the northernmost populations are currently in North Yorkshire (at Robin Hood's Bay), but the colonisation is ongoing, aided by climate change and by long-winged forms that appear once population density is high.

A mating pair of Roesel's Bush-crickets. The female is much larger and above, whilst the male hangs underneath the female.

A female eating the spermatophyllax.

Red Admiral at windfall fruit

Any sunny spell of weather these days and you are likely to come across a Red Admiral, basking or  nectaring on flowering Ivy. Red Admirals are generalist butterflies and late flowering Buddleia, Asters or other late blooming bushes will be used too. Red Admirals are also partial to fruit, and rotting, windfall pears or apples attract many individuals. Last week, a pear and an apple tree at a car park provided a glut of food for Red Admirals and wasps alike. About a dozen Red Admirals were around, either feeding on the fruit under the trees, wings closed, or basking on leaves with their wings fully open. Wasps were also feeding on the fruit, but the butterflies were not keen on sharing their table, so every time a wasp got too close the Red Admiral flicked its wings open (top shot) and flushed it out.

A basking fresh individual.

Ivy bees in Hull

 I have spent some time watching mature Ivies lately. It is Ivy peak flowering season, and the couple last days have been warm and sunny, bringing the insects out, the ivies humming with insect activity. Droneflies, Red Admirals, Comma, Wasps, honeybees are attracted to flowering bees. I was actually looking for Green Mesh Weavers, on an Ivy in an untarmaced tenfoot (alleys between houses) when I noticed two stripy bees rummaging around the leaf litter at the bottom of the ivy. I couldn't believe they were Ivy Bees, Colletes hederae! I have previously seen Ivy Bees in east Yorkshire, at North Ferriby and at Flamborough, but I thought we wouldn't get them in Hull due to our clay soils, as this bee needs loose soils for nesting. 

Two bees exploring the soil under the ivy, this is probably loose enough and sunny enough for a nest site?

A winner from climate change

Ivy Bees started colonising the UK from 2001, after expanding in northern Europe, and in the last couple of decades its distribution range has rapidly expanded northwards, with the first Scottish records coming in 2021. The mail pollen source for its larvae is Ivy, and the bee flight period coincides with the flowering season of ivy, from September to early November, with a single brood. They are solitary bees but they tend to nest together, sometimes forming large nesting aggregations in suitable habitat. Females will excavate a nest and line the walls with a cellophane-like substance, which explains another name of the bee, Cellophane Ivy Bee. Ivy pollen is brought to the nest and an egg is laid atop a mound of pollen, before the cell is sealed and another load of pollen is collected for the next egg.

One of the Ivy Bees near the ground after some exploring.

A female laden with pollen having a rest to clean its tongue.

A foraging female showing the banded abdomen. This bee is relatively large, the size of a honey bee, with orange hairs on the thorax, and contrasting broad buff bands in the abdomen, unlike its close relative the Sea Aster bee, which is smaller and has a white banded abdomen. Habitat, timing and foraging flowers can also help distinguish these bees.

The Green Meshweaver gets to Hull

 

Another post on a rapidly expanding species, this time a small spider, the Green Meshweaver, Nigma walckenaeri. All started on Saturday, during the YNU AGM in the University of Hull, where spider expert  Geoff Oxford, showed us a specimen he had just collected from the university grounds, a tiny green spider that is currently expanding its range across the UK and now colonising Yorkshire. We all admired the individual, which had been collected with its web on a leaf. 

The first Nigma walckenaeri record from Hull.

After returning from the meeting, I searched the garden ivy, and since I've been searching ivy and holly, which are favoured leaves to weave it's mesh. Nigma walckenaeri  chooses curled leaves, so it can take advantage of this to hide under its little web. As other regular character in this blog, Amaurobius, Nigma is a cribellate silk weaver. 

Today, I took a local walk and came across a magnificent mature ivy, south east facing. I started searching its leaves, wondering if I had the wrong search image in my mind. It didn't take long to find a Nigma.

Nigma walckenaeri  habitat.

There it was! A light-touch web of blueish threads with the green spider sitting, well camouflaged, underneath.

I moved part of the web aside to have a closer look (also top shot). This is a female, with her whole body green. Once I had seen one, I found another, and another, almost every ivy leaf had it's little Nigma in it. 

A male, with its brown cephalothorax.

This individual was busy weaving its web.

I even spotted a male (with reddish-brown opistosoma) on the edge of a female's web.

Until 1993 it was only found in London and the home counties, and it is associated to parks and gardens. Since then it has been steadily spreading north. I'll keep a look for it in the garden!

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!