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Species of the month

Every month it is our aim to highlight a species that is “in-season” and, although not necessarily rare or difficult to identify, has been highlighted by our local recording groups as being somewhat under-recorded and for which new records would therefore be welcomed.

If you or your recording group are aware of species such as this then please contact Bob Foreman.


June: The parasitic fly Phasia hemiptera

Phasia hemiptera - Patrick Roper

Phasia hemiptera
Photo: Patrick Roper

Phasia aurigera Andrew Thrasher

Phasia aurigera near Chichester on 20 September 2019
Photo: Andrew Thrasher

Ectophasia crassipennis - Graeme Lyons

Ectophasia crassipennis, Brighton, 2019
Photo: Graeme Lyons

Phasia hemiptera - Distribution map

Map showing scattered but widespread distribution of Phasia hemiptera records in Sussex
Source: SxBRC

Phasia hemiptera (Diptera: Tachinidae) is a large and unusual-looking fly which, in the male sex, has very distinctively shaped and coloured wings which it is suggested make it look rather like a member of the order Hemiptera (hence the specific name of the species). The females are rather smaller and darker with almost clear wings. Hemiptera is a huge order of insects ranging from shieldbugs to aphids. None, however, looks very much like Phasia hemiptera, the closest are perhaps the cicadas but there is no known link between them and P. hemiptera. I think the males look more like some beetles in flight and so, apparently, did Linnaeus when he named a similar, non-British member of the genus subcoleoptrata which means ‘almost beetle-like’. What the purpose of the sexual dimorphism and the undiptera-like appearance of the males remains, so far as I am aware, unexplained.

In their early stages these flies are endoparasitoids1 of shieldbugs (Pentatomidae), the only formally known hosts being the Green Shieldbug, Palomena prasina, the Forest Bug, Pentatoma rufipes, and the non-British Pentatoma metallica, all in the order Hemiptera although these hosts would not have been known to J. C. Fabricius when he gave P. hemiptera its specific name in 1794. Interestingly there is old Sussex record of the species (then Allophora hemiptera) in the 1905 Victoria County History which notes that a keen wildlife recorder from Bognor, H.L.F. Guermonprez, bred the fly from (presumably the larva or pupa) of a Lackey moth Malacosoma neustria from Felpham. Claude Dupuis, a leading French expert on P. hemiptera and other members the tribe Phasiini, dismissed this, however, as incroyable.

Because of the size of the flies, particularly the males, it is remarkable that there is enough nourishment, and indeed room, inside the host bugs to provide for the quite large larvae of the parasitoid. It has been recorded though that the bugs increase their normal volume after parasitisation indicating that Phasia larvae may alter the metabolism of their hosts in some way.

P. hemiptera adults are often seen in gardens, as well as in the wider countryside, on umbels of hogweed and mint flowers and the species is widely distributed in the British Isles (distribution of records in Sussex can be seen in the map). The Tachinid Recording Scheme has, however, pointed out that P. hemiptera has two lookalikes in the shape of Phasia aurigera and Ectophasia crassipennis (both of which were recorded for the first time in the UK and Sussex in 2019, P. aurigera near Chichester in West Sussex and E. crassipennis at Pett and in Brighton). P. hemiptera can be distinguished from these by the tufts of ginger hair on the sides of the thorax just behind the head.

Please record any sightings of Phasia hemiptera and other Tachinids on the iRecord website.

Patrick Roper, 16th May 2020

1 A parasite that lives inside another animal and ultimately kills it.



May: Common Starling, Sturnus vulgaris

Common Starlings at Brighton - Sandra Palme

Common Starlings at Brighton
Photo: Sandra Palme

Common Starling with nesting material - Mark Mallalieu

Common Starling with nesting material
Photo: Mark Mallalieu

As I write this, in late April, most Starlings are busily feeding their unfledged young, though one nearby pair appear to have lost their brood to a Magpie and are rebuilding their nest in the same place using bits of loose thin tree root from my garden, a by-product of my lockdown lawn enlargement. Although Starlings still use natural holes in trees and crevices in rocks to nest, many now find many suitable cavities in man-made structures, for example between the roofs and guttering of our houses. They are a widespread species across Sussex at all seasons.

My ‘lockdown walk’ takes me to a pasture 500m away, where small flocks of Starlings have been finding plenty of invertebrates, probably leatherjackets, to take back to their nests. Such feeding sites are essential for breeding Starlings. In the recent fine weather, Starlings have also been showing off their flycatching skills, with rapidly fluttering wings, glides and quick changes of direction almost (but not quite!) as agile as the flight of a hawking swallow.

When you read this, there should be lots of dowdy brown young Starlings noisily accompanying their parents on feeding forays, perhaps in your garden or on nearby fields. Have you watched Starlings searching for insect prey under a lawn? The birds have a rapid and apparently random probing technique in which they jab, then open their bills to create a small hole into which they peer with eyes rotated forward, quite unlike the deliberate “run, pause, run, sideways watch and strike” of a Blackbird. And then the Starlings are off, the whole flock launching into the air and vanishing, with no clue as to what spooked them, if anything.

Watch them as they perch on TV aerials too. Listen to their exotic array of vocalisations, often mimicking other birds. Writing this, I’ve still not seen a Swift, but I have been fooled by my local Starlings imitating a screaming Swift; and during the Hawfinch influx of 2017/18, the Starlings in the Sussex village of Fletching quickly learnt to copy the hard “tzik” of the Hawfinches that were feeding in the churchyard Yews.

Rose-coloured Starling - J Clarkson

Adult Rose-coloured Starling
Photo: John Clarkson

So the spangle-suited Starling is a real character that can give much pleasure to the locked-down naturalist. You might think that there are unlimited food sources and nesting places for them, but they have been declining in the UK, probably linked to agricultural changes and reduced areas for foraging. They are now a Red-listed species of high conservation concern. Ringing recoveries have shown that our breeding birds are augmented in winter by immigrants from eastern Europe as far away as Russia. You have probably seen, at least on television, the swirling murmurations of tens of thousands of wintering Starlings over the Somerset Levels; in Sussex, the piers used to host large roosts, including an estimated one million on Eastbourne pier in January 1998. Numbers are now far lower (there is an excellent paper in the 2018 Sussex Bird Report on roosts in Brighton, written by Chris Barfield); last winter the largest Sussex roost count was of 7800 on Brighton’s Palace pier. Why the bizarre shapes in the flocks of Starlings as they move like amoebas on fast forward across the sky? It is probably a strategy to avoid predators, which in Sussex means Peregrines and Sparrowhawks, the flocks bunching tightly when threatened to make it hard for the attacker to find a target.

I hope I’m not tempting fate here, but the warm April weather brought exceptional numbers of Hoopoes to Sussex and I wonder if they will be followed by the Common Starling’s more colourful cousin, the Rose-coloured Starling, a rare visitor from eastern Europe, which sports in adult plumage a pink body and black head, wings and tail; the young are like a washed-out version of a young Common Starling. Rose-coloured Starlings do have a habit of turning up in gardens so you might get lucky.

Mark Mallalieu
Recorder Sussex Ornithological Society



April: Holly Blue Celastrina argiolus

Holly Blue - Nigel Kemp

A spring brood female Holly Blue
Photo: Nigel Kemp

Holly Blue - Nigel Symington

Holly blue underside, freckled with delicate black spots
Photo: Nigel Symington

Holly Blue distribution map

Distribution of Holly Blue records in Sussex between 2010 - 2014
Reproduced from The Butterflies of Sussex by Michael Blencowe and Neil Hulme

There are seven ‘blue’ butterfly species resident in Sussex but during a global viral pandemic the chances of seeing them all are limited. Many of them are tied to specific food plants, specialised habitats and flight times and therefore may be out of reach if you are quarantined in a two-bedroom terraced house in Haywards Heath for six months.

However, there are two ‘blues’ that are within reach of all of us during these challenging times. The Common Blue Polyommatus icarus lives up to its name. It primarily feeds on Common Bird’s-foot-trefoil Lotus corniculatus and subsequently can be found in gardens, meadows and verges where this plant grows. But for many of us struggling through this Covid-19 pandemic an even commoner sighting will be the Holly Blue Celastrina argiolus.

The Holly Blue is a true garden butterfly and the urban areas of Sussex (where most of us find ourselves trapped at the moment) are the perfect habitat for this species. Its here it finds abundant shelter and pockets of warmth amongst our territorial terrain of fences and walls. Importantly its larval foodplants, Holly Ilex aquifolium and Ivy Hedera Helix) are abundant in our residential landscape.

The Holly Blue will have spent the wet winter of 2019/2020 in the pupal stage and will be emerging around about now as part of the year’s first brood (April-June). They will feed, meet and mate and the female will search our towns for suitable egg-laying sites. In the spring they lay eggs mostly on Holly. The caterpillars munch on the flowerbuds, pupate and produce a second brood (July-September) which emerges in the summer. Females from this brood will mainly lay on a different foodplant: Ivy. In some years a small third brood flies in October.

While other blues which are strictly confined to their communities like humans during a pandemic the Holly Blue breaks all the restrictions and roams around our towns like some carefree super-spreader. You’ll most likely see it jittering around in the treetops where you’ll look up and glimpse its silvery grey underwings (unless you’re confined to a 6th storey flat in Hove where you’ll be looking down on the vivid blue of the upperwings). If it settles on a leaf, and you are lucky to get up close, you’ll see these silvery underwings are freckled with delicate black spots.

The butterfly’s population is intimately tied to a parasite - Listrodomus nycthemerus which exclusively parasitises the Holly Blue. This ichneumon wasp uses a slender ovipositor to lay eggs into the Holly Blue’s caterpillar. The wasp’s larvae feed and develop inside the caterpillar and an adult wasp emerges from the butterfly’s chrysalis. The result is a ‘boom and bust’ population cycle for the Holly Blue. The increase in the butterfly’s population is shadowed by that of the wasp until, when the wasp numbers reach their peak, the Holly Blue’s parasitised population is overwhelmed and spectacularly crashes. The wasp then has nothing to parasitise in subsequent years so, after shooting itself in one of its six feet, its population crashes too. This gives any remaining Holly Blues the chance to restock themselves... and the cycle starts again. This is why in some years you’ll see lots of Holly Blues where as in other years they seem rather scarce. Hopefully this current Human / Covid-19 situation isn’t the start of a similar boom/bust cycle. One thing’s for certain, there will be a lot of Holly Blues flying around Sussex in 2020 thinking to themselves “Where is everybody?”.

If you do see Holly Blues (or, for that matter, any other species of butterfly, aphid, moss, dragonfly, beetle, mammal, fungus, collembola, etc.) in your garden this spring, please record your sightings on the iRecord website.

Michael Blencowe
Emeritus professor of butterflyology, University of Small Dole



March: Urban gulls Larus sp.

Herring Gulls

Juvenile and adult Herring Gulls

Lesser Black-backed Gull

Lesser Black-backed Gull

Nest Site

Typical urban nest location

Out for the count with census to safeguard seabirds

Gulls are a familiar and traditional part of life in seaside towns. Often unfairly maligned by day-trippers and coastal residents alike as noisy scavengers, populations of these most misunderstood of seabirds are in decline.

There have been three censuses of breeding seabirds in Britain and Ireland since 1969. The last one, Seabird 2000, was completed in 2002. These censuses, and regular counts at the large rural colonies, have shown that Herring and Lesser Black-Backed Gull populations have plummeted, to the extent that Herring gulls are now red-listed as 60% of the population has been lost since 1969. Lesser Black-Backed Gulls are amber-listed as their population has also seen declines.

However, these trends are based only on coastal colony counts as the first two national censuses did not cover inland or urban areas. Seabird 2000 was the first attempt to get a picture of the urban gull population, and although there were some gaps, the major areas were covered. But we do not know whether the declines in rural populations are caused in part by a shift into towns.

Given the time since Seabird 2000, it is important that another census takes place, and therefore, Seabirds Count was developed by the Seabird Monitoring Programme (SMP), and is being co-ordinated by the Joint Nature Conservation Committee (JNCC). Its goal is to gather data on numbers of breeding seabirds, with the aim of understanding how distributions and populations have changed. Survey work started in 2015, and is finished for open coastal areas. The gap that remains is to complete the survey of the urban breeding gull population.

In 2019, volunteers returned to urban areas covered by Seabird 2000 to see whether the numbers had changed. Brighton and Hove is a key area in Sussex for breeding gulls but it appears there has been a decline in numbers. 360 Herring Gull territories were recorded in Seabird 2000, but only 270 in 2019. However, it is not known whether this is due to a shift in distribution to parts of the city that were not surveyed. Anecdotally, it seems that the move to covered bins and house renovations removing chimney pots have had an impact, though if this means the gull population is as a level where it is in less conflict with residents, then this is perhaps not a bad thing.

The last phase of the urban gull census is to survey a set of randomly generated 1km squares. This is the focus of the 2020 breeding season and will enable a population estimate to be derived for the urban gull population for the first time.

The survey is simple - just one visit is needed to the survey square in late-April to late-May. The aim is to cover all the built up part of the square from the ground, and count birds incubating or holding territory. As it is difficult to see all birds from the ground, the SMP partnership has developed a correction factor for different types of urban area, which will be applied to reach a population estimate.

Gull survey squares

1km squares in Sussex that need surveying
(For full list click on link below)

There are 100 squares in East and West Sussex that need surveying ( download list here). If you would like to help, please get in touch with Alison Giacomelli ( with where you live, and she will match you up with a survey square. Thank you!



February: Pseudoscorpions

Dendrochernes cyrneus

Phoretic Large Tree-chernes, Dendrochernes cyrneus (dry decaying ancient woodland), the largest British species, on an ichneumon.
Photo: © Steve F. Woodward

Roncus lubricus

Reddish Two-eyed Chelifer, Roncus lubricus (woodland leaf litter).
Photo: © Gerald Legg

Neobisium carcinoides

Moss neobisiid, Neobisium carcinoides (leaf litter, under stones).
Photo: © Gerald Legg

Lamprochernes nodosus

Knotty Shining-claw, Lamprochernes nodosus (compost and manure heaps).
Photo: © Gerald Legg

Spermatophore of Cheiridium

Spermatophore of the Book Pseudoscorpion, Cheiridium.
Photo: © Gerald Legg

Chthonius ischnocheles

Common Chthonid, Chthonius ischnocheles (leaf litter, under stones).
Photo: © N.A. Callow

Dactylochelifer latreilli

Marram Grass Chelifer, Dactylochelifer latreillii (sand dunes, salt marshes).
Photo: © Gerald Legg

Cheiridium museorum

Book Pseudoscorpion, Cheiridium museorum (barns, warehouses, thatch, old libraries, hen-houses, stables).
Photo: © Gerald Legg

Miniature Tigers - False-scorpions

Miniature hunters resembling tiny scorpions, but without the sting-tipped tail, can be found in your garden living amongst dead leaves, under tree bark, in compost heaps even in old store rooms and thatch. Like spiders and harvestmen, they have eight legs making them arachnids, the fourth largest group: the Pseudoscorpions or false-scorpions. Worldwide there are over 2000 species of which 28 occur in the British Isles and Ireland. They are never large animals, the biggest species, which is an undescribed one from Pakistan, is only 15mm long.

As top predators they play an important role in many habitats. Several are associated with man-made habitats and have been known for a long time, for instance the ‘Book-scorpion‘ of Aristotle, that preys on book-lice that eat parts of books. As aggressive hunters they catch their prey using their enlarged and lobster-like second pair of appendages, the pedipalps. These formidable weapons vary in shape and size depending on their favoured prey: stout strong ones for tough slow prey and thin delicate ones for fast moving thinner-skinned victims. Once caught the prey may be injected with fast-acting venom and then chewed by jaws called chelicerae as digestive juices are poured into their victim. The resulting soup is then sucked-up into the mouth.

Some species are eyeless others have either one or two pairs. These are only sensitive to light levels and cannot see detail. For a pseudoscorpion to accurately navigate, find prey and mate they feel their way using special long sensory hairs: the trichobothria, many of which occur on the pedipalps and are extremely sensitive to air movements. They also occur on the rear of the animal enabling it to know what is behind it. Other sense organs detect tiny traces of chemicals - they taste the air and surroundings.

The chelicerae of some species have a special knob or longer process on the tip of the moveable ‘finger’. This ‘galea’ produces silk that is used to make silken chambers in which the animals can moult, hibernate or look after their young. Chambers can sometimes be found beneath tree bark. Mating is dangerous, as it is in many predators, and involves keeping away from the female or seducing her, as she may think a prospective mate is potentially a nice meal. So, no direct sexual contact! Sperm are transferred to the female ‘indirectly’ and often at a distance, even in the absence of the male. He produces a short silken structure called the spermatophore that he deposits on the ground and atop of which is a packet of encysted sperm which the female picks up with her genitalia. She may randomly find one or smell it out, or be directed on to it by the male. A few species perform a mating dance like scorpions do, with the male grasping the female’s palps (neutralising them thus avoiding being eaten).

An examination of the underside of the abdomen can determine the sex of an individual, males usually having a more complex and distinctive genital area than females. The female’s genitalia are designed to pick up the sperm, store it and produce fertile eggs. Young do not have distinct genital areas. Some species fertilise their eggs soon after mating whilst others store the sperm for future use. By storing sperm these species can exploit temporary habitats like a rotting log, compost heap or birds’ nest allowing a single female with eggs and sperm to start a new population. Eggs are not laid but glued together and attached to the female's genital opening and hatch as protonymphs which also remain attached and are fed with ‘milk’ produced by the mother’s ovary. The protonymphs grow and moult into deutonymphs, then moult again into tritonymphs and finally into adults. Some protonymphs are free living others remain in the silken chamber with their mother and hence they have never been seen in the wild.

To move around they just walk, but those living in transient habitats ‘hitch-hike’ - they attach themselves to flies, beetles, parasitic wasps and harvestmen and get a lift to a new habitat which may be miles away, a process known as phoresy.

To find pseudoscorpions start by getting some woodland leaf litter, spread it out it over a white sheet or tray and wait and wait ... Pseudoscorpions defend themselves from disturbance by ‘lying low’. They will usually start to move when all the other invertebrates have run off the sheet and you have decided to start again with another load of leaves! When they do appear if you gently touch the front of them you will see a defence reaction: they have a very fast reverse gear! Once spotted make a clear, no-man’s-land area, around the individual so it can be easily tracked and use a fine lightly moistened paint brush (or a small blade of licked grass) or ‘pooter’ to pick them up. For the better equipped enthusiast pseudoscorpions can be found more efficiently using a variety of standard invertebrate techniques e.g. Tullgren funnel and D-vac (a very fine collecting bag is needed as the species are tiny; relatively cheap electric garden blowers are ideal). You can view them with a x20 hand-lens and with luck be able to identify some of the commoner species. However, it is virtually impossible to identify many without the use of a binocular microscope, and in some cases even a compound microscope may be needed. Getting the lighting right will greatly improve the chance of seeing some of the features, especially the various hairs and bristles that distinguish some species. A useful guide is produced by the Field Studies Council: Pseudoscorpions, which covers 27 species; the 28th has only (2020 in press) been recently recognised - others may still be out there to discover. You can submit images and request for help to the recording group (see or the British Arachnological Society and there is a useful Facebook page too.

Pseudoscorpions can be searched for from February onward. When it is very cold, some species will vertically migrate down in the soil or into rotting wood etc. but when the weather is mild they are less likely to do so. The Sussex Biodiversity Record Centre has very few Pseudoscorpion records in the database and new ones would be very welcome. If you do find Pseudoscorpions, please send your records (with photos) to and they will be passed to the national recording scheme or, alternatively upload them to iRecord.

Gerald Legg



January: Two epiphytic liverworts

Frullania dilatata

Frullania dilatata (top) and map showing distribution of records below.
Photo: Brad Scott

Metzgeria furcata

Metzgeria furcata (top) and map showing distribution of records below.
Photomicrograph: Brad Scott

Circular patch of Frullania dilatata

Circular patch of Frullania dilatata on tree trunk.
Photo: Sue Rubinstein

Frullania_dilatata Drawing S. Rubinstein

Frullania dilatata: Dilated Scalewort, structure and detail of leaf cells.
Drawing: Sue Rubinstein

Metzgeria furcata Drawing S. Rubinstein

Metzgeria furcata: Forked Veilwort, structure and detail of thallus.
Drawing: Sue Rubinstein

When you are out and about, do have a look for some common liverworts on trees. There are two which are especially common and are likely to be in every part of Sussex. So far they have only been recorded in about half the county, and the maps are consequently more of an indication of the distribution of bryologists than the plants, so all new records are valuable.

Frullania dilatata is very distinctive, and is brown or green, often observed in neat round patches on a wide range of deciduous tree trunks. Its leaf lobes are very round and only about 1mm across.

Metzgeria furcata is also quite distinct, though there are two similar species. It is green and is forked and flat, with a strong midrib, and often found growing with Frullania dilatata. It looks like little green ribbons about 1mm wide. The two similar (though less common) species are Metzgeria violacea and Metzgeria consanguinea; they both have little granules (gemmae) either at their tips or along their margins, respectively.

We want to see how many records we can receive by the end of February, and especially how many new tetrad records there will be, so please have a look at your local trees. Please submit any records with some photos to iRecord, or with location, grid reference and date to @Trichocolea on Twitter, or by email to

There are regular field meetings recording the mosses and liverworts of the area organised by the South-East Group of the British Bryological Society, to which all are welcome, and you are encouraged to sign up to our email list. You can also follow the bryophyte recording activity in the county on our blog: